diff --git a/moto/sdb/exceptions.py b/moto/sdb/exceptions.py
index ec588d2f3..6ab6f9a3a 100644
--- a/moto/sdb/exceptions.py
+++ b/moto/sdb/exceptions.py
@@ -1,4 +1,5 @@
 """Exceptions raised by the sdb service."""
+from typing import Any
 from moto.core.exceptions import RESTError
 
 
@@ -18,7 +19,7 @@ SDB_ERROR = """<?xml version="1.0"?>
 class InvalidParameterError(RESTError):
     code = 400
 
-    def __init__(self, **kwargs):
+    def __init__(self, **kwargs: Any):
         kwargs.setdefault("template", "sdb_error")
         self.templates["sdb_error"] = SDB_ERROR
         kwargs["error_type"] = "InvalidParameterValue"
@@ -28,7 +29,7 @@ class InvalidParameterError(RESTError):
 class InvalidDomainName(InvalidParameterError):
     code = 400
 
-    def __init__(self, domain_name):
+    def __init__(self, domain_name: str):
         super().__init__(
             message=f"Value ({domain_name}) for parameter DomainName is invalid. "
         )
@@ -37,7 +38,7 @@ class InvalidDomainName(InvalidParameterError):
 class UnknownDomainName(RESTError):
     code = 400
 
-    def __init__(self, **kwargs):
+    def __init__(self, **kwargs: Any):
         kwargs.setdefault("template", "sdb_error")
         self.templates["sdb_error"] = SDB_ERROR
         kwargs["error_type"] = "NoSuchDomain"
diff --git a/moto/sdb/models.py b/moto/sdb/models.py
index 1831add4b..f093e30a8 100644
--- a/moto/sdb/models.py
+++ b/moto/sdb/models.py
@@ -1,23 +1,24 @@
 """SimpleDBBackend class with methods for supported APIs."""
 import re
 from collections import defaultdict
-from moto.core import BaseBackend, BackendDict, BaseModel
 from threading import Lock
+from typing import Any, Dict, List, Iterable, Optional
 
+from moto.core import BaseBackend, BackendDict, BaseModel
 from .exceptions import InvalidDomainName, UnknownDomainName
 
 
 class FakeItem(BaseModel):
-    def __init__(self):
-        self.attributes = []
+    def __init__(self) -> None:
+        self.attributes: List[Dict[str, Any]] = []
         self.lock = Lock()
 
-    def get_attributes(self, names):
+    def get_attributes(self, names: Optional[List[str]]) -> List[Dict[str, Any]]:
         if not names:
             return self.attributes
         return [attr for attr in self.attributes if attr["name"] in names]
 
-    def put_attributes(self, attributes):
+    def put_attributes(self, attributes: List[Dict[str, Any]]) -> None:
         # Replacing attributes involves quite a few loops
         # Lock this, so we know noone else touches this list while we're operating on it
         with self.lock:
@@ -26,56 +27,58 @@ class FakeItem(BaseModel):
                     self._remove_attributes(attr["name"])
                 self.attributes.append(attr)
 
-    def _remove_attributes(self, name):
+    def _remove_attributes(self, name: str) -> None:
         self.attributes = [attr for attr in self.attributes if attr["name"] != name]
 
 
 class FakeDomain(BaseModel):
-    def __init__(self, name):
+    def __init__(self, name: str):
         self.name = name
-        self.items = defaultdict(FakeItem)
+        self.items: Dict[str, FakeItem] = defaultdict(FakeItem)
 
-    def get(self, item_name, attribute_names):
+    def get(self, item_name: str, attribute_names: List[str]) -> List[Dict[str, Any]]:
         item = self.items[item_name]
         return item.get_attributes(attribute_names)
 
-    def put(self, item_name, attributes):
+    def put(self, item_name: str, attributes: List[Dict[str, Any]]) -> None:
         item = self.items[item_name]
         item.put_attributes(attributes)
 
 
 class SimpleDBBackend(BaseBackend):
-    def __init__(self, region_name, account_id):
+    def __init__(self, region_name: str, account_id: str):
         super().__init__(region_name, account_id)
-        self.domains = dict()
+        self.domains: Dict[str, FakeDomain] = dict()
 
-    def create_domain(self, domain_name):
+    def create_domain(self, domain_name: str) -> None:
         self._validate_domain_name(domain_name)
         self.domains[domain_name] = FakeDomain(name=domain_name)
 
-    def list_domains(self):
+    def list_domains(self) -> Iterable[str]:
         """
         The `max_number_of_domains` and `next_token` parameter have not been implemented yet - we simply return all domains.
         """
         return self.domains.keys()
 
-    def delete_domain(self, domain_name):
+    def delete_domain(self, domain_name: str) -> None:
         self._validate_domain_name(domain_name)
         # Ignore unknown domains - AWS does the same
         self.domains.pop(domain_name, None)
 
-    def _validate_domain_name(self, domain_name):
+    def _validate_domain_name(self, domain_name: str) -> None:
         # Domain Name needs to have at least 3 chars
         # Can only contain characters: a-z, A-Z, 0-9, '_', '-', and '.'
         if not re.match("^[a-zA-Z0-9-_.]{3,}$", domain_name):
             raise InvalidDomainName(domain_name)
 
-    def _get_domain(self, domain_name):
+    def _get_domain(self, domain_name: str) -> FakeDomain:
         if domain_name not in self.domains:
             raise UnknownDomainName()
         return self.domains[domain_name]
 
-    def get_attributes(self, domain_name, item_name, attribute_names):
+    def get_attributes(
+        self, domain_name: str, item_name: str, attribute_names: List[str]
+    ) -> List[Dict[str, Any]]:
         """
         Behaviour for the consistent_read-attribute is not yet implemented
         """
@@ -83,7 +86,9 @@ class SimpleDBBackend(BaseBackend):
         domain = self._get_domain(domain_name)
         return domain.get(item_name, attribute_names)
 
-    def put_attributes(self, domain_name, item_name, attributes):
+    def put_attributes(
+        self, domain_name: str, item_name: str, attributes: List[Dict[str, Any]]
+    ) -> None:
         """
         Behaviour for the expected-attribute is not yet implemented.
         """
diff --git a/moto/sdb/responses.py b/moto/sdb/responses.py
index 1e03a7d61..11b197428 100644
--- a/moto/sdb/responses.py
+++ b/moto/sdb/responses.py
@@ -1,33 +1,33 @@
 from moto.core.responses import BaseResponse
-from .models import sdb_backends
+from .models import sdb_backends, SimpleDBBackend
 
 
 class SimpleDBResponse(BaseResponse):
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__(service_name="sdb")
 
     @property
-    def sdb_backend(self):
+    def sdb_backend(self) -> SimpleDBBackend:
         return sdb_backends[self.current_account][self.region]
 
-    def create_domain(self):
+    def create_domain(self) -> str:
         domain_name = self._get_param("DomainName")
         self.sdb_backend.create_domain(domain_name=domain_name)
         template = self.response_template(CREATE_DOMAIN_TEMPLATE)
         return template.render()
 
-    def delete_domain(self):
+    def delete_domain(self) -> str:
         domain_name = self._get_param("DomainName")
         self.sdb_backend.delete_domain(domain_name=domain_name)
         template = self.response_template(DELETE_DOMAIN_TEMPLATE)
         return template.render()
 
-    def list_domains(self):
+    def list_domains(self) -> str:
         domain_names = self.sdb_backend.list_domains()
         template = self.response_template(LIST_DOMAINS_TEMPLATE)
         return template.render(domain_names=domain_names, next_token=None)
 
-    def get_attributes(self):
+    def get_attributes(self) -> str:
         domain_name = self._get_param("DomainName")
         item_name = self._get_param("ItemName")
         attribute_names = self._get_multi_param("AttributeName.")
@@ -39,7 +39,7 @@ class SimpleDBResponse(BaseResponse):
         template = self.response_template(GET_ATTRIBUTES_TEMPLATE)
         return template.render(attributes=attributes)
 
-    def put_attributes(self):
+    def put_attributes(self) -> str:
         domain_name = self._get_param("DomainName")
         item_name = self._get_param("ItemName")
         attributes = self._get_list_prefix("Attribute")
diff --git a/moto/server.py b/moto/server.py
index b451943a1..0e727d611 100644
--- a/moto/server.py
+++ b/moto/server.py
@@ -3,6 +3,7 @@ import os
 import signal
 import sys
 import warnings
+from typing import Any, List, Optional
 
 from werkzeug.serving import run_simple
 
@@ -15,11 +16,11 @@ from moto.moto_server.threaded_moto_server import (  # noqa # pylint: disable=un
 )
 
 
-def signal_handler(signum, frame):  # pylint: disable=unused-argument
+def signal_handler(signum: Any, frame: Any) -> None:  # pylint: disable=unused-argument
     sys.exit(0)
 
 
-def main(argv=None):
+def main(argv: Optional[List[str]] = None) -> None:
     argv = argv or sys.argv[1:]
     parser = argparse.ArgumentParser()
 
@@ -79,9 +80,9 @@ def main(argv=None):
 
     # Wrap the main application
     main_app = DomainDispatcherApplication(create_backend_app, service=args.service)
-    main_app.debug = True
+    main_app.debug = True  # type: ignore
 
-    ssl_context = None
+    ssl_context: Any = None
     if args.ssl_key and args.ssl_cert:
         ssl_context = (args.ssl_cert, args.ssl_key)
     elif args.ssl:
diff --git a/moto/servicediscovery/exceptions.py b/moto/servicediscovery/exceptions.py
index f816fcc2c..4615306f3 100644
--- a/moto/servicediscovery/exceptions.py
+++ b/moto/servicediscovery/exceptions.py
@@ -3,20 +3,20 @@ from moto.core.exceptions import JsonRESTError
 
 
 class OperationNotFound(JsonRESTError):
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__("OperationNotFound", "")
 
 
 class NamespaceNotFound(JsonRESTError):
-    def __init__(self, ns_id):
+    def __init__(self, ns_id: str):
         super().__init__("NamespaceNotFound", f"{ns_id}")
 
 
 class ServiceNotFound(JsonRESTError):
-    def __init__(self, ns_id):
+    def __init__(self, ns_id: str):
         super().__init__("ServiceNotFound", f"{ns_id}")
 
 
 class ConflictingDomainExists(JsonRESTError):
-    def __init__(self, vpc_id):
+    def __init__(self, vpc_id: str):
         super().__init__("ConflictingDomainExists", f"{vpc_id}")
diff --git a/moto/servicediscovery/models.py b/moto/servicediscovery/models.py
index a97ab294a..2841011ec 100644
--- a/moto/servicediscovery/models.py
+++ b/moto/servicediscovery/models.py
@@ -1,4 +1,5 @@
 import string
+from typing import Any, Dict, Iterable, List, Optional
 
 from moto.core import BaseBackend, BackendDict, BaseModel
 from moto.core.utils import unix_time
@@ -13,7 +14,7 @@ from .exceptions import (
 )
 
 
-def random_id(size):
+def random_id(size: int) -> str:
     return "".join(
         [random.choice(string.ascii_lowercase + string.digits) for _ in range(size)]
     )
@@ -22,17 +23,16 @@ def random_id(size):
 class Namespace(BaseModel):
     def __init__(
         self,
-        account_id,
-        region,
-        name,
-        ns_type,
-        creator_request_id,
-        description,
-        dns_properties,
-        http_properties,
-        vpc=None,
+        account_id: str,
+        region: str,
+        name: str,
+        ns_type: str,
+        creator_request_id: str,
+        description: str,
+        dns_properties: Dict[str, Any],
+        http_properties: Dict[str, Any],
+        vpc: Optional[str] = None,
     ):
-        super().__init__()
         self.id = f"ns-{random_id(20)}"
         self.arn = f"arn:aws:servicediscovery:{region}:{account_id}:namespace/{self.id}"
         self.name = name
@@ -45,7 +45,7 @@ class Namespace(BaseModel):
         self.created = unix_time()
         self.updated = unix_time()
 
-    def to_json(self):
+    def to_json(self) -> Dict[str, Any]:
         return {
             "Arn": self.arn,
             "Id": self.id,
@@ -65,31 +65,30 @@ class Namespace(BaseModel):
 class Service(BaseModel):
     def __init__(
         self,
-        account_id,
-        region,
-        name,
-        namespace_id,
-        description,
-        creator_request_id,
-        dns_config,
-        health_check_config,
-        health_check_custom_config,
-        service_type,
+        account_id: str,
+        region: str,
+        name: str,
+        namespace_id: str,
+        description: str,
+        creator_request_id: str,
+        dns_config: Dict[str, Any],
+        health_check_config: Dict[str, Any],
+        health_check_custom_config: Dict[str, int],
+        service_type: str,
     ):
-        super().__init__()
         self.id = f"srv-{random_id(8)}"
         self.arn = f"arn:aws:servicediscovery:{region}:{account_id}:service/{self.id}"
         self.name = name
         self.namespace_id = namespace_id
         self.description = description
         self.creator_request_id = creator_request_id
-        self.dns_config = dns_config
+        self.dns_config: Optional[Dict[str, Any]] = dns_config
         self.health_check_config = health_check_config
         self.health_check_custom_config = health_check_custom_config
         self.service_type = service_type
         self.created = unix_time()
 
-    def update(self, details):
+    def update(self, details: Dict[str, Any]) -> None:
         if "Description" in details:
             self.description = details["Description"]
         if "DnsConfig" in details:
@@ -104,7 +103,7 @@ class Service(BaseModel):
         if "HealthCheckConfig" in details:
             self.health_check_config = details["HealthCheckConfig"]
 
-    def to_json(self):
+    def to_json(self) -> Dict[str, Any]:
         return {
             "Arn": self.arn,
             "Id": self.id,
@@ -121,7 +120,7 @@ class Service(BaseModel):
 
 
 class Operation(BaseModel):
-    def __init__(self, operation_type, targets):
+    def __init__(self, operation_type: str, targets: Dict[str, str]):
         super().__init__()
         self.id = f"{random_id(32)}-{random_id(8)}"
         self.status = "SUCCESS"
@@ -130,7 +129,7 @@ class Operation(BaseModel):
         self.updated = unix_time()
         self.targets = targets
 
-    def to_json(self, short=False):
+    def to_json(self, short: bool = False) -> Dict[str, Any]:
         if short:
             return {"Id": self.id, "Status": self.status}
         else:
@@ -147,20 +146,26 @@ class Operation(BaseModel):
 class ServiceDiscoveryBackend(BaseBackend):
     """Implementation of ServiceDiscovery APIs."""
 
-    def __init__(self, region_name, account_id):
+    def __init__(self, region_name: str, account_id: str):
         super().__init__(region_name, account_id)
-        self.operations = dict()
-        self.namespaces = dict()
-        self.services = dict()
+        self.operations: Dict[str, Operation] = dict()
+        self.namespaces: Dict[str, Namespace] = dict()
+        self.services: Dict[str, Service] = dict()
         self.tagger = TaggingService()
 
-    def list_namespaces(self):
+    def list_namespaces(self) -> Iterable[Namespace]:
         """
         Pagination or the Filters-parameter is not yet implemented
         """
         return self.namespaces.values()
 
-    def create_http_namespace(self, name, creator_request_id, description, tags):
+    def create_http_namespace(
+        self,
+        name: str,
+        creator_request_id: str,
+        description: str,
+        tags: List[Dict[str, str]],
+    ) -> str:
         namespace = Namespace(
             account_id=self.account_id,
             region=self.region_name,
@@ -179,13 +184,12 @@ class ServiceDiscoveryBackend(BaseBackend):
         )
         return operation_id
 
-    def _create_operation(self, op_type, targets):
+    def _create_operation(self, op_type: str, targets: Dict[str, str]) -> str:
         operation = Operation(operation_type=op_type, targets=targets)
         self.operations[operation.id] = operation
-        operation_id = operation.id
-        return operation_id
+        return operation.id
 
-    def delete_namespace(self, namespace_id):
+    def delete_namespace(self, namespace_id: str) -> str:
         if namespace_id not in self.namespaces:
             raise NamespaceNotFound(namespace_id)
         del self.namespaces[namespace_id]
@@ -194,12 +198,12 @@ class ServiceDiscoveryBackend(BaseBackend):
         )
         return operation_id
 
-    def get_namespace(self, namespace_id):
+    def get_namespace(self, namespace_id: str) -> Namespace:
         if namespace_id not in self.namespaces:
             raise NamespaceNotFound(namespace_id)
         return self.namespaces[namespace_id]
 
-    def list_operations(self):
+    def list_operations(self) -> Iterable[Operation]:
         """
         Pagination or the Filters-argument is not yet implemented
         """
@@ -211,23 +215,31 @@ class ServiceDiscoveryBackend(BaseBackend):
         }
         return self.operations.values()
 
-    def get_operation(self, operation_id):
+    def get_operation(self, operation_id: str) -> Operation:
         if operation_id not in self.operations:
             raise OperationNotFound()
         return self.operations[operation_id]
 
-    def tag_resource(self, resource_arn, tags):
+    def tag_resource(self, resource_arn: str, tags: List[Dict[str, str]]) -> None:
         self.tagger.tag_resource(resource_arn, tags)
 
-    def untag_resource(self, resource_arn, tag_keys):
+    def untag_resource(self, resource_arn: str, tag_keys: List[str]) -> None:
         self.tagger.untag_resource_using_names(resource_arn, tag_keys)
 
-    def list_tags_for_resource(self, resource_arn):
+    def list_tags_for_resource(
+        self, resource_arn: str
+    ) -> Dict[str, List[Dict[str, str]]]:
         return self.tagger.list_tags_for_resource(resource_arn)
 
     def create_private_dns_namespace(
-        self, name, creator_request_id, description, vpc, tags, properties
-    ):
+        self,
+        name: str,
+        creator_request_id: str,
+        description: str,
+        vpc: str,
+        tags: List[Dict[str, str]],
+        properties: Dict[str, Any],
+    ) -> str:
         for namespace in self.namespaces.values():
             if namespace.vpc == vpc:
                 raise ConflictingDomainExists(vpc)
@@ -253,8 +265,13 @@ class ServiceDiscoveryBackend(BaseBackend):
         return operation_id
 
     def create_public_dns_namespace(
-        self, name, creator_request_id, description, tags, properties
-    ):
+        self,
+        name: str,
+        creator_request_id: str,
+        description: str,
+        tags: List[Dict[str, str]],
+        properties: Dict[str, Any],
+    ) -> str:
         dns_properties = (properties or {}).get("DnsProperties", {})
         dns_properties["HostedZoneId"] = "hzi"
         namespace = Namespace(
@@ -277,16 +294,16 @@ class ServiceDiscoveryBackend(BaseBackend):
 
     def create_service(
         self,
-        name,
-        namespace_id,
-        creator_request_id,
-        description,
-        dns_config,
-        health_check_config,
-        health_check_custom_config,
-        tags,
-        service_type,
-    ):
+        name: str,
+        namespace_id: str,
+        creator_request_id: str,
+        description: str,
+        dns_config: Dict[str, Any],
+        health_check_config: Dict[str, Any],
+        health_check_custom_config: Dict[str, Any],
+        tags: List[Dict[str, str]],
+        service_type: str,
+    ) -> Service:
         service = Service(
             account_id=self.account_id,
             region=self.region_name,
@@ -304,21 +321,21 @@ class ServiceDiscoveryBackend(BaseBackend):
             self.tagger.tag_resource(service.arn, tags)
         return service
 
-    def get_service(self, service_id):
+    def get_service(self, service_id: str) -> Service:
         if service_id not in self.services:
             raise ServiceNotFound(service_id)
         return self.services[service_id]
 
-    def delete_service(self, service_id):
+    def delete_service(self, service_id: str) -> None:
         self.services.pop(service_id, None)
 
-    def list_services(self):
+    def list_services(self) -> Iterable[Service]:
         """
         Pagination or the Filters-argument is not yet implemented
         """
         return self.services.values()
 
-    def update_service(self, service_id, details):
+    def update_service(self, service_id: str, details: Dict[str, Any]) -> str:
         service = self.get_service(service_id)
         service.update(details=details)
         operation_id = self._create_operation(
diff --git a/moto/servicediscovery/responses.py b/moto/servicediscovery/responses.py
index 55d43fe7a..972b9d532 100644
--- a/moto/servicediscovery/responses.py
+++ b/moto/servicediscovery/responses.py
@@ -1,24 +1,25 @@
 """Handles incoming servicediscovery requests, invokes methods, returns responses."""
 import json
 
+from moto.core.common_types import TYPE_RESPONSE
 from moto.core.responses import BaseResponse
-from .models import servicediscovery_backends
+from .models import servicediscovery_backends, ServiceDiscoveryBackend
 
 
 class ServiceDiscoveryResponse(BaseResponse):
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__(service_name="servicediscovery")
 
     @property
-    def servicediscovery_backend(self):
+    def servicediscovery_backend(self) -> ServiceDiscoveryBackend:
         """Return backend instance specific for this region."""
         return servicediscovery_backends[self.current_account][self.region]
 
-    def list_namespaces(self):
+    def list_namespaces(self) -> TYPE_RESPONSE:
         namespaces = self.servicediscovery_backend.list_namespaces()
         return 200, {}, json.dumps({"Namespaces": [ns.to_json() for ns in namespaces]})
 
-    def create_http_namespace(self):
+    def create_http_namespace(self) -> str:
         params = json.loads(self.body)
         name = params.get("Name")
         creator_request_id = params.get("CreatorRequestId")
@@ -32,7 +33,7 @@ class ServiceDiscoveryResponse(BaseResponse):
         )
         return json.dumps(dict(OperationId=operation_id))
 
-    def delete_namespace(self):
+    def delete_namespace(self) -> str:
         params = json.loads(self.body)
         namespace_id = params.get("Id")
         operation_id = self.servicediscovery_backend.delete_namespace(
@@ -40,7 +41,7 @@ class ServiceDiscoveryResponse(BaseResponse):
         )
         return json.dumps(dict(OperationId=operation_id))
 
-    def list_operations(self):
+    def list_operations(self) -> TYPE_RESPONSE:
         operations = self.servicediscovery_backend.list_operations()
         return (
             200,
@@ -48,7 +49,7 @@ class ServiceDiscoveryResponse(BaseResponse):
             json.dumps({"Operations": [o.to_json(short=True) for o in operations]}),
         )
 
-    def get_operation(self):
+    def get_operation(self) -> str:
         params = json.loads(self.body)
         operation_id = params.get("OperationId")
         operation = self.servicediscovery_backend.get_operation(
@@ -56,7 +57,7 @@ class ServiceDiscoveryResponse(BaseResponse):
         )
         return json.dumps(dict(Operation=operation.to_json()))
 
-    def get_namespace(self):
+    def get_namespace(self) -> str:
         params = json.loads(self.body)
         namespace_id = params.get("Id")
         namespace = self.servicediscovery_backend.get_namespace(
@@ -64,23 +65,23 @@ class ServiceDiscoveryResponse(BaseResponse):
         )
         return json.dumps(dict(Namespace=namespace.to_json()))
 
-    def tag_resource(self):
+    def tag_resource(self) -> str:
         params = json.loads(self.body)
         resource_arn = params.get("ResourceARN")
         tags = params.get("Tags")
         self.servicediscovery_backend.tag_resource(resource_arn=resource_arn, tags=tags)
-        return json.dumps(dict())
+        return "{}"
 
-    def untag_resource(self):
+    def untag_resource(self) -> str:
         params = json.loads(self.body)
         resource_arn = params.get("ResourceARN")
         tag_keys = params.get("TagKeys")
         self.servicediscovery_backend.untag_resource(
             resource_arn=resource_arn, tag_keys=tag_keys
         )
-        return json.dumps(dict())
+        return "{}"
 
-    def list_tags_for_resource(self):
+    def list_tags_for_resource(self) -> TYPE_RESPONSE:
         params = json.loads(self.body)
         resource_arn = params.get("ResourceARN")
         tags = self.servicediscovery_backend.list_tags_for_resource(
@@ -88,7 +89,7 @@ class ServiceDiscoveryResponse(BaseResponse):
         )
         return 200, {}, json.dumps(tags)
 
-    def create_private_dns_namespace(self):
+    def create_private_dns_namespace(self) -> str:
         params = json.loads(self.body)
         name = params.get("Name")
         creator_request_id = params.get("CreatorRequestId")
@@ -106,7 +107,7 @@ class ServiceDiscoveryResponse(BaseResponse):
         )
         return json.dumps(dict(OperationId=operation_id))
 
-    def create_public_dns_namespace(self):
+    def create_public_dns_namespace(self) -> str:
         params = json.loads(self.body)
         name = params.get("Name")
         creator_request_id = params.get("CreatorRequestId")
@@ -122,7 +123,7 @@ class ServiceDiscoveryResponse(BaseResponse):
         )
         return json.dumps(dict(OperationId=operation_id))
 
-    def create_service(self):
+    def create_service(self) -> str:
         params = json.loads(self.body)
         name = params.get("Name")
         namespace_id = params.get("NamespaceId")
@@ -146,23 +147,23 @@ class ServiceDiscoveryResponse(BaseResponse):
         )
         return json.dumps(dict(Service=service.to_json()))
 
-    def get_service(self):
+    def get_service(self) -> str:
         params = json.loads(self.body)
         service_id = params.get("Id")
         service = self.servicediscovery_backend.get_service(service_id=service_id)
         return json.dumps(dict(Service=service.to_json()))
 
-    def delete_service(self):
+    def delete_service(self) -> str:
         params = json.loads(self.body)
         service_id = params.get("Id")
         self.servicediscovery_backend.delete_service(service_id=service_id)
-        return json.dumps(dict())
+        return "{}"
 
-    def list_services(self):
+    def list_services(self) -> str:
         services = self.servicediscovery_backend.list_services()
         return json.dumps(dict(Services=[s.to_json() for s in services]))
 
-    def update_service(self):
+    def update_service(self) -> str:
         params = json.loads(self.body)
         service_id = params.get("Id")
         details = params.get("Service")
diff --git a/moto/settings.py b/moto/settings.py
index a84803df1..5ca0e6b13 100644
--- a/moto/settings.py
+++ b/moto/settings.py
@@ -38,7 +38,7 @@ SKIP_REQUIRES_DOCKER = bool(os.environ.get("TESTS_SKIP_REQUIRES_DOCKER", False))
 LAMBDA_DATA_DIR = os.environ.get("MOTO_LAMBDA_DATA_DIR", "/tmp/data")
 
 
-def get_sf_execution_history_type():
+def get_sf_execution_history_type() -> str:
     """
     Determines which execution history events `get_execution_history` returns
     :returns: str representing the type of Step Function Execution Type events should be
@@ -97,11 +97,11 @@ def moto_lambda_image() -> str:
     return os.environ.get("MOTO_DOCKER_LAMBDA_IMAGE", "mlupin/docker-lambda")
 
 
-def moto_network_name() -> str:
+def moto_network_name() -> Optional[str]:
     return os.environ.get("MOTO_DOCKER_NETWORK_NAME")
 
 
-def moto_network_mode() -> str:
+def moto_network_mode() -> Optional[str]:
     return os.environ.get("MOTO_DOCKER_NETWORK_MODE")
 
 
diff --git a/moto/signer/models.py b/moto/signer/models.py
index 7289362f6..59395db54 100644
--- a/moto/signer/models.py
+++ b/moto/signer/models.py
@@ -1,10 +1,18 @@
+from typing import Any, Dict, List, Optional
+
 from moto.core import BaseBackend, BackendDict, BaseModel
 from moto.moto_api._internal import mock_random
 
 
 class SigningProfile(BaseModel):
     def __init__(
-        self, account_id, region, name, platform_id, signature_validity_period, tags
+        self,
+        account_id: str,
+        region: str,
+        name: str,
+        platform_id: str,
+        signature_validity_period: Optional[Dict[str, Any]],
+        tags: Dict[str, str],
     ):
         self.name = name
         self.platform_id = platform_id
@@ -19,11 +27,11 @@ class SigningProfile(BaseModel):
         self.profile_version = mock_random.get_random_hex(10)
         self.profile_version_arn = f"{self.arn}/{self.profile_version}"
 
-    def cancel(self):
+    def cancel(self) -> None:
         self.status = "Canceled"
 
-    def to_dict(self, full=True):
-        small = {
+    def to_dict(self, full: bool = True) -> Dict[str, Any]:
+        small: Dict[str, Any] = {
             "arn": self.arn,
             "profileVersion": self.profile_version,
             "profileVersionArn": self.profile_version_arn,
@@ -149,22 +157,22 @@ class SignerBackend(BaseBackend):
         },
     ]
 
-    def __init__(self, region_name, account_id):
+    def __init__(self, region_name: str, account_id: str):
         super().__init__(region_name, account_id)
-        self.signing_profiles: [str, SigningProfile] = dict()
+        self.signing_profiles: Dict[str, SigningProfile] = dict()
 
-    def cancel_signing_profile(self, profile_name) -> None:
+    def cancel_signing_profile(self, profile_name: str) -> None:
         self.signing_profiles[profile_name].cancel()
 
-    def get_signing_profile(self, profile_name) -> SigningProfile:
+    def get_signing_profile(self, profile_name: str) -> SigningProfile:
         return self.signing_profiles[profile_name]
 
     def put_signing_profile(
         self,
-        profile_name,
-        signature_validity_period,
-        platform_id,
-        tags,
+        profile_name: str,
+        signature_validity_period: Optional[Dict[str, Any]],
+        platform_id: str,
+        tags: Dict[str, str],
     ) -> SigningProfile:
         """
         The following parameters are not yet implemented: SigningMaterial, Overrides, SigningParamaters
@@ -180,7 +188,7 @@ class SignerBackend(BaseBackend):
         self.signing_profiles[profile_name] = profile
         return profile
 
-    def list_signing_platforms(self):
+    def list_signing_platforms(self) -> List[Dict[str, Any]]:
         """
         Pagination is not yet implemented. The parameters category, partner, target are not yet implemented
         """
@@ -189,4 +197,4 @@ class SignerBackend(BaseBackend):
 
 # Using the lambda-regions
 # boto3.Session().get_available_regions("signer") still returns an empty list
-signer_backends: [str, [str, SignerBackend]] = BackendDict(SignerBackend, "lambda")
+signer_backends = BackendDict(SignerBackend, "lambda")
diff --git a/moto/signer/responses.py b/moto/signer/responses.py
index ad42aa587..86073dc48 100644
--- a/moto/signer/responses.py
+++ b/moto/signer/responses.py
@@ -6,7 +6,7 @@ from .models import signer_backends, SignerBackend
 
 
 class signerResponse(BaseResponse):
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__(service_name="signer")
 
     @property
@@ -14,17 +14,17 @@ class signerResponse(BaseResponse):
         """Return backend instance specific for this region."""
         return signer_backends[self.current_account][self.region]
 
-    def cancel_signing_profile(self):
+    def cancel_signing_profile(self) -> str:
         profile_name = self.path.split("/")[-1]
         self.signer_backend.cancel_signing_profile(profile_name=profile_name)
         return "{}"
 
-    def get_signing_profile(self):
+    def get_signing_profile(self) -> str:
         profile_name = self.path.split("/")[-1]
         profile = self.signer_backend.get_signing_profile(profile_name=profile_name)
         return json.dumps(profile.to_dict())
 
-    def put_signing_profile(self):
+    def put_signing_profile(self) -> str:
         params = json.loads(self.body)
         profile_name = self.path.split("/")[-1]
         signature_validity_period = params.get("signatureValidityPeriod")
@@ -38,6 +38,6 @@ class signerResponse(BaseResponse):
         )
         return json.dumps(profile.to_dict(full=False))
 
-    def list_signing_platforms(self):
+    def list_signing_platforms(self) -> str:
         platforms = self.signer_backend.list_signing_platforms()
         return json.dumps(dict(platforms=platforms))
diff --git a/moto/ssoadmin/exceptions.py b/moto/ssoadmin/exceptions.py
index a133e1d5e..990eaa5de 100644
--- a/moto/ssoadmin/exceptions.py
+++ b/moto/ssoadmin/exceptions.py
@@ -3,5 +3,5 @@ from moto.core.exceptions import JsonRESTError
 
 
 class ResourceNotFound(JsonRESTError):
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__("ResourceNotFound", "Account not found")
diff --git a/moto/ssoadmin/models.py b/moto/ssoadmin/models.py
index 0aeba130c..d83c96147 100644
--- a/moto/ssoadmin/models.py
+++ b/moto/ssoadmin/models.py
@@ -1,21 +1,22 @@
-from .exceptions import ResourceNotFound
+from typing import Any, Dict, List
 
 from moto.core import BaseBackend, BackendDict, BaseModel
 from moto.core.utils import unix_time
 from moto.moto_api._internal import mock_random as random
 from moto.utilities.paginator import paginate
+from .exceptions import ResourceNotFound
 from .utils import PAGINATION_MODEL
 
 
 class AccountAssignment(BaseModel):
     def __init__(
         self,
-        instance_arn,
-        target_id,
-        target_type,
-        permission_set_arn,
-        principal_type,
-        principal_id,
+        instance_arn: str,
+        target_id: str,
+        target_type: str,
+        permission_set_arn: str,
+        principal_type: str,
+        principal_id: str,
     ):
         self.request_id = str(random.uuid4())
         self.instance_arn = instance_arn
@@ -26,8 +27,8 @@ class AccountAssignment(BaseModel):
         self.principal_id = principal_id
         self.created_date = unix_time()
 
-    def to_json(self, include_creation_date=False):
-        summary = {
+    def to_json(self, include_creation_date: bool = False) -> Dict[str, Any]:
+        summary: Dict[str, Any] = {
             "TargetId": self.target_id,
             "TargetType": self.target_type,
             "PermissionSetArn": self.permission_set_arn,
@@ -42,12 +43,12 @@ class AccountAssignment(BaseModel):
 class PermissionSet(BaseModel):
     def __init__(
         self,
-        name,
-        description,
-        instance_arn,
-        session_duration,
-        relay_state,
-        tags,
+        name: str,
+        description: str,
+        instance_arn: str,
+        session_duration: str,
+        relay_state: str,
+        tags: List[Dict[str, str]],
     ):
         self.name = name
         self.description = description
@@ -58,8 +59,8 @@ class PermissionSet(BaseModel):
         self.tags = tags
         self.created_date = unix_time()
 
-    def to_json(self, include_creation_date=False):
-        summary = {
+    def to_json(self, include_creation_date: bool = False) -> Dict[str, Any]:
+        summary: Dict[str, Any] = {
             "Name": self.name,
             "Description": self.description,
             "PermissionSetArn": self.permission_set_arn,
@@ -71,7 +72,7 @@ class PermissionSet(BaseModel):
         return summary
 
     @staticmethod
-    def generate_id(instance_arn):
+    def generate_id(instance_arn: str) -> str:
         chars = list(range(10)) + ["a", "b", "c", "d", "e", "f"]
         return (
             instance_arn
@@ -83,20 +84,20 @@ class PermissionSet(BaseModel):
 class SSOAdminBackend(BaseBackend):
     """Implementation of SSOAdmin APIs."""
 
-    def __init__(self, region_name, account_id):
+    def __init__(self, region_name: str, account_id: str):
         super().__init__(region_name, account_id)
-        self.account_assignments = list()
-        self.permission_sets = list()
+        self.account_assignments: List[AccountAssignment] = list()
+        self.permission_sets: List[PermissionSet] = list()
 
     def create_account_assignment(
         self,
-        instance_arn,
-        target_id,
-        target_type,
-        permission_set_arn,
-        principal_type,
-        principal_id,
-    ):
+        instance_arn: str,
+        target_id: str,
+        target_type: str,
+        permission_set_arn: str,
+        principal_type: str,
+        principal_id: str,
+    ) -> Dict[str, Any]:
         assignment = AccountAssignment(
             instance_arn,
             target_id,
@@ -110,13 +111,13 @@ class SSOAdminBackend(BaseBackend):
 
     def delete_account_assignment(
         self,
-        instance_arn,
-        target_id,
-        target_type,
-        permission_set_arn,
-        principal_type,
-        principal_id,
-    ):
+        instance_arn: str,
+        target_id: str,
+        target_type: str,
+        permission_set_arn: str,
+        principal_type: str,
+        principal_id: str,
+    ) -> Dict[str, Any]:
         account = self._find_account(
             instance_arn,
             target_id,
@@ -130,13 +131,13 @@ class SSOAdminBackend(BaseBackend):
 
     def _find_account(
         self,
-        instance_arn,
-        target_id,
-        target_type,
-        permission_set_arn,
-        principal_type,
-        principal_id,
-    ):
+        instance_arn: str,
+        target_id: str,
+        target_type: str,
+        permission_set_arn: str,
+        principal_type: str,
+        principal_id: str,
+    ) -> AccountAssignment:
         for account in self.account_assignments:
             instance_arn_match = account.instance_arn == instance_arn
             target_id_match = account.target_id == target_id
@@ -155,7 +156,9 @@ class SSOAdminBackend(BaseBackend):
                 return account
         raise ResourceNotFound
 
-    def list_account_assignments(self, instance_arn, account_id, permission_set_arn):
+    def list_account_assignments(
+        self, instance_arn: str, account_id: str, permission_set_arn: str
+    ) -> List[Dict[str, Any]]:
         """
         Pagination has not yet been implemented
         """
@@ -178,13 +181,13 @@ class SSOAdminBackend(BaseBackend):
 
     def create_permission_set(
         self,
-        name,
-        description,
-        instance_arn,
-        session_duration,
-        relay_state,
-        tags,
-    ):
+        name: str,
+        description: str,
+        instance_arn: str,
+        session_duration: str,
+        relay_state: str,
+        tags: List[Dict[str, str]],
+    ) -> Dict[str, Any]:
         permission_set = PermissionSet(
             name,
             description,
@@ -198,12 +201,12 @@ class SSOAdminBackend(BaseBackend):
 
     def update_permission_set(
         self,
-        instance_arn,
-        permission_set_arn,
-        description,
-        session_duration,
-        relay_state,
-    ):
+        instance_arn: str,
+        permission_set_arn: str,
+        description: str,
+        session_duration: str,
+        relay_state: str,
+    ) -> Dict[str, Any]:
         permission_set = self._find_permission_set(
             instance_arn,
             permission_set_arn,
@@ -216,10 +219,8 @@ class SSOAdminBackend(BaseBackend):
         return permission_set.to_json(True)
 
     def describe_permission_set(
-        self,
-        instance_arn,
-        permission_set_arn,
-    ):
+        self, instance_arn: str, permission_set_arn: str
+    ) -> Dict[str, Any]:
         permission_set = self._find_permission_set(
             instance_arn,
             permission_set_arn,
@@ -227,10 +228,8 @@ class SSOAdminBackend(BaseBackend):
         return permission_set.to_json(True)
 
     def delete_permission_set(
-        self,
-        instance_arn,
-        permission_set_arn,
-    ):
+        self, instance_arn: str, permission_set_arn: str
+    ) -> Dict[str, Any]:
         permission_set = self._find_permission_set(
             instance_arn,
             permission_set_arn,
@@ -239,10 +238,8 @@ class SSOAdminBackend(BaseBackend):
         return permission_set.to_json(include_creation_date=True)
 
     def _find_permission_set(
-        self,
-        instance_arn,
-        permission_set_arn,
-    ):
+        self, instance_arn: str, permission_set_arn: str
+    ) -> PermissionSet:
         for permission_set in self.permission_sets:
             instance_arn_match = permission_set.instance_arn == instance_arn
             permission_set_match = (
@@ -253,7 +250,7 @@ class SSOAdminBackend(BaseBackend):
         raise ResourceNotFound
 
     @paginate(pagination_model=PAGINATION_MODEL)
-    def list_permission_sets(self, instance_arn):
+    def list_permission_sets(self, instance_arn: str) -> List[PermissionSet]:  # type: ignore[misc]
         permission_sets = []
         for permission_set in self.permission_sets:
             if permission_set.instance_arn == instance_arn:
diff --git a/moto/ssoadmin/responses.py b/moto/ssoadmin/responses.py
index 83ad84388..7276a71ce 100644
--- a/moto/ssoadmin/responses.py
+++ b/moto/ssoadmin/responses.py
@@ -3,21 +3,21 @@ import json
 from moto.core.responses import BaseResponse
 from moto.moto_api._internal import mock_random
 
-from .models import ssoadmin_backends
+from .models import ssoadmin_backends, SSOAdminBackend
 
 
 class SSOAdminResponse(BaseResponse):
     """Handler for SSOAdmin requests and responses."""
 
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__(service_name="sso-admin")
 
     @property
-    def ssoadmin_backend(self):
+    def ssoadmin_backend(self) -> SSOAdminBackend:
         """Return backend instance specific for this region."""
         return ssoadmin_backends[self.current_account][self.region]
 
-    def create_account_assignment(self):
+    def create_account_assignment(self) -> str:
         params = json.loads(self.body)
         instance_arn = params.get("InstanceArn")
         target_id = params.get("TargetId")
@@ -37,7 +37,7 @@ class SSOAdminResponse(BaseResponse):
         summary["RequestId"] = str(mock_random.uuid4())
         return json.dumps({"AccountAssignmentCreationStatus": summary})
 
-    def delete_account_assignment(self):
+    def delete_account_assignment(self) -> str:
         params = json.loads(self.body)
         instance_arn = params.get("InstanceArn")
         target_id = params.get("TargetId")
@@ -57,7 +57,7 @@ class SSOAdminResponse(BaseResponse):
         summary["RequestId"] = str(mock_random.uuid4())
         return json.dumps({"AccountAssignmentDeletionStatus": summary})
 
-    def list_account_assignments(self):
+    def list_account_assignments(self) -> str:
         params = json.loads(self.body)
         instance_arn = params.get("InstanceArn")
         account_id = params.get("AccountId")
@@ -69,7 +69,7 @@ class SSOAdminResponse(BaseResponse):
         )
         return json.dumps({"AccountAssignments": assignments})
 
-    def create_permission_set(self):
+    def create_permission_set(self) -> str:
         name = self._get_param("Name")
         description = self._get_param("Description")
         instance_arn = self._get_param("InstanceArn")
@@ -88,7 +88,7 @@ class SSOAdminResponse(BaseResponse):
 
         return json.dumps({"PermissionSet": permission_set})
 
-    def delete_permission_set(self):
+    def delete_permission_set(self) -> str:
         params = json.loads(self.body)
         instance_arn = params.get("InstanceArn")
         permission_set_arn = params.get("PermissionSetArn")
@@ -96,8 +96,9 @@ class SSOAdminResponse(BaseResponse):
             instance_arn=instance_arn,
             permission_set_arn=permission_set_arn,
         )
+        return "{}"
 
-    def update_permission_set(self):
+    def update_permission_set(self) -> str:
         instance_arn = self._get_param("InstanceArn")
         permission_set_arn = self._get_param("PermissionSetArn")
         description = self._get_param("Description")
@@ -111,8 +112,9 @@ class SSOAdminResponse(BaseResponse):
             session_duration=session_duration,
             relay_state=relay_state,
         )
+        return "{}"
 
-    def describe_permission_set(self):
+    def describe_permission_set(self) -> str:
         instance_arn = self._get_param("InstanceArn")
         permission_set_arn = self._get_param("PermissionSetArn")
 
@@ -122,7 +124,7 @@ class SSOAdminResponse(BaseResponse):
         )
         return json.dumps({"PermissionSet": permission_set})
 
-    def list_permission_sets(self):
+    def list_permission_sets(self) -> str:
         instance_arn = self._get_param("InstanceArn")
         max_results = self._get_int_param("MaxResults")
         next_token = self._get_param("NextToken")
diff --git a/moto/stepfunctions/exceptions.py b/moto/stepfunctions/exceptions.py
index eae9dc1e8..b7e449a54 100644
--- a/moto/stepfunctions/exceptions.py
+++ b/moto/stepfunctions/exceptions.py
@@ -35,7 +35,7 @@ class InvalidToken(AWSError):
     TYPE = "InvalidToken"
     STATUS = 400
 
-    def __init__(self, message="Invalid token"):
+    def __init__(self, message: str = "Invalid token"):
         super().__init__(f"Invalid Token: {message}")
 
 
@@ -43,5 +43,5 @@ class ResourceNotFound(AWSError):
     TYPE = "ResourceNotFound"
     STATUS = 400
 
-    def __init__(self, arn):
+    def __init__(self, arn: str):
         super().__init__(f"Resource not found: '{arn}'")
diff --git a/moto/stepfunctions/models.py b/moto/stepfunctions/models.py
index 64d4eea45..5628c95dd 100644
--- a/moto/stepfunctions/models.py
+++ b/moto/stepfunctions/models.py
@@ -2,6 +2,7 @@ import json
 import re
 from datetime import datetime
 from dateutil.tz import tzlocal
+from typing import Any, Dict, List, Iterable, Optional, Pattern
 
 from moto.core import BaseBackend, BackendDict, CloudFormationModel
 from moto.core.utils import iso_8601_datetime_with_milliseconds
@@ -21,19 +22,32 @@ from moto.utilities.paginator import paginate
 
 
 class StateMachine(CloudFormationModel):
-    def __init__(self, arn, name, definition, roleArn, tags=None):
+    def __init__(
+        self,
+        arn: str,
+        name: str,
+        definition: str,
+        roleArn: str,
+        tags: Optional[List[Dict[str, str]]] = None,
+    ):
         self.creation_date = iso_8601_datetime_with_milliseconds(datetime.now())
         self.update_date = self.creation_date
         self.arn = arn
         self.name = name
         self.definition = definition
         self.roleArn = roleArn
-        self.executions = []
-        self.tags = []
+        self.executions: List[Execution] = []
+        self.tags: List[Dict[str, str]] = []
         if tags:
             self.add_tags(tags)
 
-    def start_execution(self, region_name, account_id, execution_name, execution_input):
+    def start_execution(
+        self,
+        region_name: str,
+        account_id: str,
+        execution_name: str,
+        execution_input: str,
+    ) -> "Execution":
         self._ensure_execution_name_doesnt_exist(execution_name)
         self._validate_execution_input(execution_input)
         execution = Execution(
@@ -47,7 +61,7 @@ class StateMachine(CloudFormationModel):
         self.executions.append(execution)
         return execution
 
-    def stop_execution(self, execution_arn):
+    def stop_execution(self, execution_arn: str) -> "Execution":
         execution = next(
             (x for x in self.executions if x.execution_arn == execution_arn), None
         )
@@ -58,14 +72,14 @@ class StateMachine(CloudFormationModel):
         execution.stop()
         return execution
 
-    def _ensure_execution_name_doesnt_exist(self, name):
+    def _ensure_execution_name_doesnt_exist(self, name: str) -> None:
         for execution in self.executions:
             if execution.name == name:
                 raise ExecutionAlreadyExists(
                     "Execution Already Exists: '" + execution.execution_arn + "'"
                 )
 
-    def _validate_execution_input(self, execution_input):
+    def _validate_execution_input(self, execution_input: str) -> None:
         try:
             json.loads(execution_input)
         except Exception as ex:
@@ -73,13 +87,13 @@ class StateMachine(CloudFormationModel):
                 "Invalid State Machine Execution Input: '" + str(ex) + "'"
             )
 
-    def update(self, **kwargs):
+    def update(self, **kwargs: Any) -> None:
         for key, value in kwargs.items():
             if value is not None:
                 setattr(self, key, value)
         self.update_date = iso_8601_datetime_with_milliseconds(datetime.now())
 
-    def add_tags(self, tags):
+    def add_tags(self, tags: List[Dict[str, str]]) -> List[Dict[str, str]]:
         merged_tags = []
         for tag in self.tags:
             replacement_index = next(
@@ -96,15 +110,15 @@ class StateMachine(CloudFormationModel):
         self.tags = merged_tags
         return self.tags
 
-    def remove_tags(self, tag_keys):
+    def remove_tags(self, tag_keys: List[str]) -> List[Dict[str, str]]:
         self.tags = [tag_set for tag_set in self.tags if tag_set["key"] not in tag_keys]
         return self.tags
 
     @property
-    def physical_resource_id(self):
+    def physical_resource_id(self) -> str:
         return self.arn
 
-    def get_cfn_properties(self, prop_overrides):
+    def get_cfn_properties(self, prop_overrides: Dict[str, Any]) -> Dict[str, Any]:
         property_names = [
             "DefinitionString",
             "RoleArn",
@@ -124,7 +138,7 @@ class StateMachine(CloudFormationModel):
         return properties
 
     @classmethod
-    def has_cfn_attr(cls, attr):
+    def has_cfn_attr(cls, attr: str) -> bool:
         return attr in [
             "Name",
             "DefinitionString",
@@ -133,7 +147,7 @@ class StateMachine(CloudFormationModel):
             "Tags",
         ]
 
-    def get_cfn_attribute(self, attribute_name):
+    def get_cfn_attribute(self, attribute_name: str) -> Any:
         from moto.cloudformation.exceptions import UnformattedGetAttTemplateException
 
         if attribute_name == "Name":
@@ -150,17 +164,22 @@ class StateMachine(CloudFormationModel):
         raise UnformattedGetAttTemplateException()
 
     @staticmethod
-    def cloudformation_name_type():
+    def cloudformation_name_type() -> str:
         return "StateMachine"
 
     @staticmethod
-    def cloudformation_type():
+    def cloudformation_type() -> str:
         return "AWS::StepFunctions::StateMachine"
 
     @classmethod
-    def create_from_cloudformation_json(
-        cls, resource_name, cloudformation_json, account_id, region_name, **kwargs
-    ):
+    def create_from_cloudformation_json(  # type: ignore[misc]
+        cls,
+        resource_name: str,
+        cloudformation_json: Any,
+        account_id: str,
+        region_name: str,
+        **kwargs: Any,
+    ) -> "StateMachine":
         properties = cloudformation_json["Properties"]
         name = properties.get("StateMachineName", resource_name)
         definition = properties.get("DefinitionString", "")
@@ -170,19 +189,25 @@ class StateMachine(CloudFormationModel):
         return sf_backend.create_state_machine(name, definition, role_arn, tags=tags)
 
     @classmethod
-    def delete_from_cloudformation_json(cls, resource_name, _, account_id, region_name):
+    def delete_from_cloudformation_json(  # type: ignore[misc]
+        cls,
+        resource_name: str,
+        cloudformation_json: Any,
+        account_id: str,
+        region_name: str,
+    ) -> None:
         sf_backend = stepfunction_backends[account_id][region_name]
         sf_backend.delete_state_machine(resource_name)
 
     @classmethod
-    def update_from_cloudformation_json(
+    def update_from_cloudformation_json(  # type: ignore[misc]
         cls,
-        original_resource,
-        new_resource_name,
-        cloudformation_json,
-        account_id,
-        region_name,
-    ):
+        original_resource: Any,
+        new_resource_name: str,
+        cloudformation_json: Any,
+        account_id: str,
+        region_name: str,
+    ) -> "StateMachine":
         properties = cloudformation_json.get("Properties", {})
         name = properties.get("StateMachineName", original_resource.name)
 
@@ -214,12 +239,12 @@ class StateMachine(CloudFormationModel):
 class Execution:
     def __init__(
         self,
-        region_name,
-        account_id,
-        state_machine_name,
-        execution_name,
-        state_machine_arn,
-        execution_input,
+        region_name: str,
+        account_id: str,
+        state_machine_name: str,
+        execution_name: str,
+        state_machine_arn: str,
+        execution_input: str,
     ):
         execution_arn = "arn:aws:states:{}:{}:execution:{}:{}"
         execution_arn = execution_arn.format(
@@ -235,9 +260,9 @@ class Execution:
             if settings.get_sf_execution_history_type() == "SUCCESS"
             else "FAILED"
         )
-        self.stop_date = None
+        self.stop_date: Optional[str] = None
 
-    def get_execution_history(self, roleArn):
+    def get_execution_history(self, roleArn: str) -> List[Dict[str, Any]]:
         sf_execution_history_type = settings.get_sf_execution_history_type()
         if sf_execution_history_type == "SUCCESS":
             return [
@@ -334,8 +359,9 @@ class Execution:
                     },
                 },
             ]
+        return []
 
-    def stop(self):
+    def stop(self) -> None:
         self.status = "ABORTED"
         self.stop_date = iso_8601_datetime_with_milliseconds(datetime.now())
 
@@ -451,13 +477,19 @@ class StepFunctionBackend(BaseBackend):
         "arn:aws:states:[-0-9a-zA-Z]+:(?P<account_id>[0-9]{12}):execution:.+"
     )
 
-    def __init__(self, region_name, account_id):
+    def __init__(self, region_name: str, account_id: str):
         super().__init__(region_name, account_id)
-        self.state_machines = []
-        self.executions = []
+        self.state_machines: List[StateMachine] = []
+        self.executions: List[Execution] = []
         self._account_id = None
 
-    def create_state_machine(self, name, definition, roleArn, tags=None):
+    def create_state_machine(
+        self,
+        name: str,
+        definition: str,
+        roleArn: str,
+        tags: Optional[List[Dict[str, str]]] = None,
+    ) -> StateMachine:
         self._validate_name(name)
         self._validate_role_arn(roleArn)
         arn = f"arn:aws:states:{self.region_name}:{self.account_id}:stateMachine:{name}"
@@ -469,11 +501,10 @@ class StepFunctionBackend(BaseBackend):
             return state_machine
 
     @paginate(pagination_model=PAGINATION_MODEL)
-    def list_state_machines(self):
-        state_machines = sorted(self.state_machines, key=lambda x: x.creation_date)
-        return state_machines
+    def list_state_machines(self) -> Iterable[StateMachine]:  # type: ignore[misc]
+        return sorted(self.state_machines, key=lambda x: x.creation_date)
 
-    def describe_state_machine(self, arn):
+    def describe_state_machine(self, arn: str) -> StateMachine:
         self._validate_machine_arn(arn)
         sm = next((x for x in self.state_machines if x.arn == arn), None)
         if not sm:
@@ -482,13 +513,15 @@ class StepFunctionBackend(BaseBackend):
             )
         return sm
 
-    def delete_state_machine(self, arn):
+    def delete_state_machine(self, arn: str) -> None:
         self._validate_machine_arn(arn)
         sm = next((x for x in self.state_machines if x.arn == arn), None)
         if sm:
             self.state_machines.remove(sm)
 
-    def update_state_machine(self, arn, definition=None, role_arn=None):
+    def update_state_machine(
+        self, arn: str, definition: Optional[str] = None, role_arn: Optional[str] = None
+    ) -> StateMachine:
         sm = self.describe_state_machine(arn)
         updates = {
             "definition": definition,
@@ -497,23 +530,24 @@ class StepFunctionBackend(BaseBackend):
         sm.update(**updates)
         return sm
 
-    def start_execution(self, state_machine_arn, name=None, execution_input=None):
+    def start_execution(
+        self, state_machine_arn: str, name: str, execution_input: str
+    ) -> Execution:
         state_machine = self.describe_state_machine(state_machine_arn)
-        execution = state_machine.start_execution(
+        return state_machine.start_execution(
             region_name=self.region_name,
             account_id=self.account_id,
             execution_name=name or str(mock_random.uuid4()),
             execution_input=execution_input,
         )
-        return execution
 
-    def stop_execution(self, execution_arn):
+    def stop_execution(self, execution_arn: str) -> Execution:
         self._validate_execution_arn(execution_arn)
         state_machine = self._get_state_machine_for_execution(execution_arn)
         return state_machine.stop_execution(execution_arn)
 
     @paginate(pagination_model=PAGINATION_MODEL)
-    def list_executions(self, state_machine_arn, status_filter=None):
+    def list_executions(self, state_machine_arn: str, status_filter: Optional[str] = None) -> Iterable[Execution]:  # type: ignore[misc]
         """
         The status of every execution is set to 'RUNNING' by default.
         Set the following environment variable if you want to get a FAILED status back:
@@ -530,7 +564,7 @@ class StepFunctionBackend(BaseBackend):
         executions = sorted(executions, key=lambda x: x.start_date, reverse=True)
         return executions
 
-    def describe_execution(self, execution_arn):
+    def describe_execution(self, execution_arn: str) -> Execution:
         """
         The status of every execution is set to 'RUNNING' by default.
         Set the following environment variable if you want to get a FAILED status back:
@@ -551,7 +585,7 @@ class StepFunctionBackend(BaseBackend):
             )
         return exctn
 
-    def get_execution_history(self, execution_arn):
+    def get_execution_history(self, execution_arn: str) -> List[Dict[str, Any]]:
         """
         A static list of successful events is returned by default.
         Set the following environment variable if you want to get a static list of events for a failed execution:
@@ -572,61 +606,61 @@ class StepFunctionBackend(BaseBackend):
             )
         return execution.get_execution_history(state_machine.roleArn)
 
-    def list_tags_for_resource(self, arn):
+    def list_tags_for_resource(self, arn: str) -> List[Dict[str, str]]:
         try:
             state_machine = self.describe_state_machine(arn)
             return state_machine.tags or []
         except StateMachineDoesNotExist:
             return []
 
-    def tag_resource(self, resource_arn, tags):
+    def tag_resource(self, resource_arn: str, tags: List[Dict[str, str]]) -> None:
         try:
             state_machine = self.describe_state_machine(resource_arn)
             state_machine.add_tags(tags)
         except StateMachineDoesNotExist:
             raise ResourceNotFound(resource_arn)
 
-    def untag_resource(self, resource_arn, tag_keys):
+    def untag_resource(self, resource_arn: str, tag_keys: List[str]) -> None:
         try:
             state_machine = self.describe_state_machine(resource_arn)
             state_machine.remove_tags(tag_keys)
         except StateMachineDoesNotExist:
             raise ResourceNotFound(resource_arn)
 
-    def _validate_name(self, name):
+    def _validate_name(self, name: str) -> None:
         if any(invalid_char in name for invalid_char in self.invalid_chars_for_name):
             raise InvalidName("Invalid Name: '" + name + "'")
 
         if any(name.find(char) >= 0 for char in self.invalid_unicodes_for_name):
             raise InvalidName("Invalid Name: '" + name + "'")
 
-    def _validate_role_arn(self, role_arn):
+    def _validate_role_arn(self, role_arn: str) -> None:
         self._validate_arn(
             arn=role_arn,
             regex=self.accepted_role_arn_format,
             invalid_msg="Invalid Role Arn: '" + role_arn + "'",
         )
 
-    def _validate_machine_arn(self, machine_arn):
+    def _validate_machine_arn(self, machine_arn: str) -> None:
         self._validate_arn(
             arn=machine_arn,
             regex=self.accepted_mchn_arn_format,
             invalid_msg="Invalid State Machine Arn: '" + machine_arn + "'",
         )
 
-    def _validate_execution_arn(self, execution_arn):
+    def _validate_execution_arn(self, execution_arn: str) -> None:
         self._validate_arn(
             arn=execution_arn,
             regex=self.accepted_exec_arn_format,
             invalid_msg="Execution Does Not Exist: '" + execution_arn + "'",
         )
 
-    def _validate_arn(self, arn, regex, invalid_msg):
+    def _validate_arn(self, arn: str, regex: Pattern[str], invalid_msg: str) -> None:
         match = regex.match(arn)
         if not arn or not match:
             raise InvalidArn(invalid_msg)
 
-    def _get_state_machine_for_execution(self, execution_arn):
+    def _get_state_machine_for_execution(self, execution_arn: str) -> StateMachine:
         state_machine_name = execution_arn.split(":")[6]
         state_machine_arn = next(
             (x.arn for x in self.state_machines if x.name == state_machine_name), None
diff --git a/moto/stepfunctions/responses.py b/moto/stepfunctions/responses.py
index d13b14ee5..cf68b83bf 100644
--- a/moto/stepfunctions/responses.py
+++ b/moto/stepfunctions/responses.py
@@ -1,20 +1,21 @@
 import json
 
+from moto.core.common_types import TYPE_RESPONSE
 from moto.core.responses import BaseResponse
 from moto.utilities.aws_headers import amzn_request_id
-from .models import stepfunction_backends
+from .models import stepfunction_backends, StepFunctionBackend
 
 
 class StepFunctionResponse(BaseResponse):
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__(service_name="stepfunctions")
 
     @property
-    def stepfunction_backend(self):
+    def stepfunction_backend(self) -> StepFunctionBackend:
         return stepfunction_backends[self.current_account][self.region]
 
     @amzn_request_id
-    def create_state_machine(self):
+    def create_state_machine(self) -> TYPE_RESPONSE:
         name = self._get_param("name")
         definition = self._get_param("definition")
         roleArn = self._get_param("roleArn")
@@ -29,7 +30,7 @@ class StepFunctionResponse(BaseResponse):
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def list_state_machines(self):
+    def list_state_machines(self) -> TYPE_RESPONSE:
         max_results = self._get_int_param("maxResults")
         next_token = self._get_param("nextToken")
         results, next_token = self.stepfunction_backend.list_state_machines(
@@ -49,12 +50,12 @@ class StepFunctionResponse(BaseResponse):
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def describe_state_machine(self):
+    def describe_state_machine(self) -> TYPE_RESPONSE:
         arn = self._get_param("stateMachineArn")
         return self._describe_state_machine(arn)
 
     @amzn_request_id
-    def _describe_state_machine(self, state_machine_arn):
+    def _describe_state_machine(self, state_machine_arn: str) -> TYPE_RESPONSE:
         state_machine = self.stepfunction_backend.describe_state_machine(
             state_machine_arn
         )
@@ -69,13 +70,13 @@ class StepFunctionResponse(BaseResponse):
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def delete_state_machine(self):
+    def delete_state_machine(self) -> TYPE_RESPONSE:
         arn = self._get_param("stateMachineArn")
         self.stepfunction_backend.delete_state_machine(arn)
         return 200, {}, json.dumps("{}")
 
     @amzn_request_id
-    def update_state_machine(self):
+    def update_state_machine(self) -> TYPE_RESPONSE:
         arn = self._get_param("stateMachineArn")
         definition = self._get_param("definition")
         role_arn = self._get_param("roleArn")
@@ -88,28 +89,28 @@ class StepFunctionResponse(BaseResponse):
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def list_tags_for_resource(self):
+    def list_tags_for_resource(self) -> TYPE_RESPONSE:
         arn = self._get_param("resourceArn")
         tags = self.stepfunction_backend.list_tags_for_resource(arn)
         response = {"tags": tags}
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def tag_resource(self):
+    def tag_resource(self) -> TYPE_RESPONSE:
         arn = self._get_param("resourceArn")
         tags = self._get_param("tags", [])
         self.stepfunction_backend.tag_resource(arn, tags)
         return 200, {}, json.dumps({})
 
     @amzn_request_id
-    def untag_resource(self):
+    def untag_resource(self) -> TYPE_RESPONSE:
         arn = self._get_param("resourceArn")
         tag_keys = self._get_param("tagKeys", [])
         self.stepfunction_backend.untag_resource(arn, tag_keys)
         return 200, {}, json.dumps({})
 
     @amzn_request_id
-    def start_execution(self):
+    def start_execution(self) -> TYPE_RESPONSE:
         arn = self._get_param("stateMachineArn")
         name = self._get_param("name")
         execution_input = self._get_param("input", if_none="{}")
@@ -123,7 +124,7 @@ class StepFunctionResponse(BaseResponse):
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def list_executions(self):
+    def list_executions(self) -> TYPE_RESPONSE:
         max_results = self._get_int_param("maxResults")
         next_token = self._get_param("nextToken")
         arn = self._get_param("stateMachineArn")
@@ -151,7 +152,7 @@ class StepFunctionResponse(BaseResponse):
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def describe_execution(self):
+    def describe_execution(self) -> TYPE_RESPONSE:
         arn = self._get_param("executionArn")
         execution = self.stepfunction_backend.describe_execution(arn)
         response = {
@@ -166,20 +167,20 @@ class StepFunctionResponse(BaseResponse):
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def describe_state_machine_for_execution(self):
+    def describe_state_machine_for_execution(self) -> TYPE_RESPONSE:
         arn = self._get_param("executionArn")
         execution = self.stepfunction_backend.describe_execution(arn)
         return self._describe_state_machine(execution.state_machine_arn)
 
     @amzn_request_id
-    def stop_execution(self):
+    def stop_execution(self) -> TYPE_RESPONSE:
         arn = self._get_param("executionArn")
         execution = self.stepfunction_backend.stop_execution(arn)
         response = {"stopDate": execution.stop_date}
         return 200, {}, json.dumps(response)
 
     @amzn_request_id
-    def get_execution_history(self):
+    def get_execution_history(self) -> TYPE_RESPONSE:
         execution_arn = self._get_param("executionArn")
         execution_history = self.stepfunction_backend.get_execution_history(
             execution_arn
diff --git a/moto/stepfunctions/utils.py b/moto/stepfunctions/utils.py
index 20881771f..db9aa1f36 100644
--- a/moto/stepfunctions/utils.py
+++ b/moto/stepfunctions/utils.py
@@ -1,3 +1,6 @@
+from typing import Dict, List
+
+
 PAGINATION_MODEL = {
     "list_executions": {
         "input_token": "next_token",
@@ -14,11 +17,9 @@ PAGINATION_MODEL = {
 }
 
 
-def cfn_to_api_tags(cfn_tags_entry):
-    api_tags = [{k.lower(): v for k, v in d.items()} for d in cfn_tags_entry]
-    return api_tags
+def cfn_to_api_tags(cfn_tags_entry: List[Dict[str, str]]) -> List[Dict[str, str]]:
+    return [{k.lower(): v for k, v in d.items()} for d in cfn_tags_entry]
 
 
-def api_to_cfn_tags(api_tags):
-    cfn_tags_entry = [{k.capitalize(): v for k, v in d.items()} for d in api_tags]
-    return cfn_tags_entry
+def api_to_cfn_tags(api_tags: List[Dict[str, str]]) -> List[Dict[str, str]]:
+    return [{k.capitalize(): v for k, v in d.items()} for d in api_tags]
diff --git a/moto/sts/exceptions.py b/moto/sts/exceptions.py
index 021945f9f..6f136af2d 100644
--- a/moto/sts/exceptions.py
+++ b/moto/sts/exceptions.py
@@ -1,3 +1,4 @@
+from typing import Any
 from moto.core.exceptions import RESTError
 
 
@@ -6,5 +7,5 @@ class STSClientError(RESTError):
 
 
 class STSValidationError(STSClientError):
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args: Any, **kwargs: Any):
         super().__init__("ValidationError", *args, **kwargs)
diff --git a/moto/sts/models.py b/moto/sts/models.py
index bf0641b55..c60525415 100644
--- a/moto/sts/models.py
+++ b/moto/sts/models.py
@@ -1,10 +1,12 @@
 from base64 import b64decode
+from typing import Any, Dict, List, Optional, Tuple
 import datetime
 import re
 import xmltodict
+
 from moto.core import BaseBackend, BaseModel, BackendDict
 from moto.core.utils import iso_8601_datetime_with_milliseconds
-from moto.iam import iam_backends
+from moto.iam.models import iam_backends, AccessKey
 from moto.sts.utils import (
     random_session_token,
     DEFAULT_STS_SESSION_DURATION,
@@ -13,27 +15,27 @@ from moto.sts.utils import (
 
 
 class Token(BaseModel):
-    def __init__(self, duration, name=None):
+    def __init__(self, duration: int, name: Optional[str] = None):
         now = datetime.datetime.utcnow()
         self.expiration = now + datetime.timedelta(seconds=duration)
         self.name = name
         self.policy = None
 
     @property
-    def expiration_ISO8601(self):
+    def expiration_ISO8601(self) -> str:
         return iso_8601_datetime_with_milliseconds(self.expiration)
 
 
 class AssumedRole(BaseModel):
     def __init__(
         self,
-        account_id,
-        access_key,
-        role_session_name,
-        role_arn,
-        policy,
-        duration,
-        external_id,
+        account_id: str,
+        access_key: AccessKey,
+        role_session_name: str,
+        role_arn: str,
+        policy: str,
+        duration: int,
+        external_id: str,
     ):
         self.account_id = account_id
         self.session_name = role_session_name
@@ -48,11 +50,11 @@ class AssumedRole(BaseModel):
         self.session_token = random_session_token()
 
     @property
-    def expiration_ISO8601(self):
+    def expiration_ISO8601(self) -> str:
         return iso_8601_datetime_with_milliseconds(self.expiration)
 
     @property
-    def user_id(self):
+    def user_id(self) -> str:
         iam_backend = iam_backends[self.account_id]["global"]
         try:
             role_id = iam_backend.get_role_by_arn(arn=self.role_arn).id
@@ -61,31 +63,38 @@ class AssumedRole(BaseModel):
         return role_id + ":" + self.session_name
 
     @property
-    def arn(self):
+    def arn(self) -> str:
         return f"arn:aws:sts::{self.account_id}:assumed-role/{self.role_arn.split('/')[-1]}/{self.session_name}"
 
 
 class STSBackend(BaseBackend):
-    def __init__(self, region_name, account_id):
+    def __init__(self, region_name: str, account_id: str):
         super().__init__(region_name, account_id)
-        self.assumed_roles = []
+        self.assumed_roles: List[AssumedRole] = []
 
     @staticmethod
-    def default_vpc_endpoint_service(service_region, zones):
+    def default_vpc_endpoint_service(
+        service_region: str, zones: List[str]
+    ) -> List[Dict[str, str]]:
         """Default VPC endpoint service."""
         return BaseBackend.default_vpc_endpoint_service_factory(
             service_region, zones, "sts"
         )
 
-    def get_session_token(self, duration):
-        token = Token(duration=duration)
-        return token
+    def get_session_token(self, duration: int) -> Token:
+        return Token(duration=duration)
 
-    def get_federation_token(self, name, duration):
-        token = Token(duration=duration, name=name)
-        return token
+    def get_federation_token(self, name: Optional[str], duration: int) -> Token:
+        return Token(duration=duration, name=name)
 
-    def assume_role(self, role_session_name, role_arn, policy, duration, external_id):
+    def assume_role(
+        self,
+        role_session_name: str,
+        role_arn: str,
+        policy: str,
+        duration: int,
+        external_id: str,
+    ) -> AssumedRole:
         """
         Assume an IAM Role. Note that the role does not need to exist. The ARN can point to another account, providing an opportunity to switch accounts.
         """
@@ -103,16 +112,18 @@ class STSBackend(BaseBackend):
         account_backend.assumed_roles.append(role)
         return role
 
-    def get_assumed_role_from_access_key(self, access_key_id):
+    def get_assumed_role_from_access_key(
+        self, access_key_id: str
+    ) -> Optional[AssumedRole]:
         for assumed_role in self.assumed_roles:
             if assumed_role.access_key_id == access_key_id:
                 return assumed_role
         return None
 
-    def assume_role_with_web_identity(self, **kwargs):
+    def assume_role_with_web_identity(self, **kwargs: Any) -> AssumedRole:
         return self.assume_role(**kwargs)
 
-    def assume_role_with_saml(self, **kwargs):
+    def assume_role_with_saml(self, **kwargs: Any) -> AssumedRole:
         del kwargs["principal_arn"]
         saml_assertion_encoded = kwargs.pop("saml_assertion")
         saml_assertion_decoded = b64decode(saml_assertion_encoded)
@@ -150,7 +161,7 @@ class STSBackend(BaseBackend):
         if "duration" not in kwargs:
             kwargs["duration"] = DEFAULT_STS_SESSION_DURATION
 
-        account_id, access_key = self._create_access_key(role=target_role)
+        account_id, access_key = self._create_access_key(role=target_role)  # type: ignore
         kwargs["account_id"] = account_id
         kwargs["access_key"] = access_key
 
@@ -160,7 +171,7 @@ class STSBackend(BaseBackend):
         self.assumed_roles.append(role)
         return role
 
-    def get_caller_identity(self, access_key_id):
+    def get_caller_identity(self, access_key_id: str) -> Tuple[str, str, str]:
         assumed_role = self.get_assumed_role_from_access_key(access_key_id)
         if assumed_role:
             return assumed_role.user_id, assumed_role.arn, assumed_role.account_id
@@ -175,7 +186,7 @@ class STSBackend(BaseBackend):
         arn = f"arn:aws:sts::{self.account_id}:user/moto"
         return user_id, arn, self.account_id
 
-    def _create_access_key(self, role):
+    def _create_access_key(self, role: str) -> Tuple[str, AccessKey]:
         account_id_match = re.search(r"arn:aws:iam::([0-9]+).+", role)
         if account_id_match:
             account_id = account_id_match.group(1)
diff --git a/moto/sts/responses.py b/moto/sts/responses.py
index d6099566d..c54481652 100644
--- a/moto/sts/responses.py
+++ b/moto/sts/responses.py
@@ -1,25 +1,25 @@
 from moto.core.responses import BaseResponse
 from .exceptions import STSValidationError
-from .models import sts_backends
+from .models import sts_backends, STSBackend
 
 MAX_FEDERATION_TOKEN_POLICY_LENGTH = 2048
 
 
 class TokenResponse(BaseResponse):
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__(service_name="sts")
 
     @property
-    def backend(self):
+    def backend(self) -> STSBackend:
         return sts_backends[self.current_account]["global"]
 
-    def get_session_token(self):
+    def get_session_token(self) -> str:
         duration = int(self.querystring.get("DurationSeconds", [43200])[0])
         token = self.backend.get_session_token(duration=duration)
         template = self.response_template(GET_SESSION_TOKEN_RESPONSE)
         return template.render(token=token)
 
-    def get_federation_token(self):
+    def get_federation_token(self) -> str:
         duration = int(self.querystring.get("DurationSeconds", [43200])[0])
         policy = self.querystring.get("Policy", [None])[0]
 
@@ -31,14 +31,14 @@ class TokenResponse(BaseResponse):
                 f" equal to {MAX_FEDERATION_TOKEN_POLICY_LENGTH}"
             )
 
-        name = self.querystring.get("Name")[0]
+        name = self.querystring.get("Name")[0]  # type: ignore
         token = self.backend.get_federation_token(duration=duration, name=name)
         template = self.response_template(GET_FEDERATION_TOKEN_RESPONSE)
         return template.render(token=token, account_id=self.current_account)
 
-    def assume_role(self):
-        role_session_name = self.querystring.get("RoleSessionName")[0]
-        role_arn = self.querystring.get("RoleArn")[0]
+    def assume_role(self) -> str:
+        role_session_name = self.querystring.get("RoleSessionName")[0]  # type: ignore
+        role_arn = self.querystring.get("RoleArn")[0]  # type: ignore
 
         policy = self.querystring.get("Policy", [None])[0]
         duration = int(self.querystring.get("DurationSeconds", [3600])[0])
@@ -54,9 +54,9 @@ class TokenResponse(BaseResponse):
         template = self.response_template(ASSUME_ROLE_RESPONSE)
         return template.render(role=role)
 
-    def assume_role_with_web_identity(self):
-        role_session_name = self.querystring.get("RoleSessionName")[0]
-        role_arn = self.querystring.get("RoleArn")[0]
+    def assume_role_with_web_identity(self) -> str:
+        role_session_name = self.querystring.get("RoleSessionName")[0]  # type: ignore
+        role_arn = self.querystring.get("RoleArn")[0]  # type: ignore
 
         policy = self.querystring.get("Policy", [None])[0]
         duration = int(self.querystring.get("DurationSeconds", [3600])[0])
@@ -72,10 +72,10 @@ class TokenResponse(BaseResponse):
         template = self.response_template(ASSUME_ROLE_WITH_WEB_IDENTITY_RESPONSE)
         return template.render(role=role)
 
-    def assume_role_with_saml(self):
-        role_arn = self.querystring.get("RoleArn")[0]
-        principal_arn = self.querystring.get("PrincipalArn")[0]
-        saml_assertion = self.querystring.get("SAMLAssertion")[0]
+    def assume_role_with_saml(self) -> str:
+        role_arn = self.querystring.get("RoleArn")[0]  # type: ignore
+        principal_arn = self.querystring.get("PrincipalArn")[0]  # type: ignore
+        saml_assertion = self.querystring.get("SAMLAssertion")[0]  # type: ignore
 
         role = self.backend.assume_role_with_saml(
             role_arn=role_arn,
@@ -85,7 +85,7 @@ class TokenResponse(BaseResponse):
         template = self.response_template(ASSUME_ROLE_WITH_SAML_RESPONSE)
         return template.render(role=role)
 
-    def get_caller_identity(self):
+    def get_caller_identity(self) -> str:
         template = self.response_template(GET_CALLER_IDENTITY_RESPONSE)
 
         access_key_id = self.get_access_key()
diff --git a/moto/sts/utils.py b/moto/sts/utils.py
index afd095796..c2149146f 100644
--- a/moto/sts/utils.py
+++ b/moto/sts/utils.py
@@ -16,13 +16,13 @@ def random_session_token() -> str:
     )
 
 
-def random_assumed_role_id():
+def random_assumed_role_id() -> str:
     return (
         ACCOUNT_SPECIFIC_ASSUMED_ROLE_ID_PREFIX + _random_uppercase_or_digit_sequence(9)
     )
 
 
-def _random_uppercase_or_digit_sequence(length):
+def _random_uppercase_or_digit_sequence(length: int) -> str:
     return "".join(
         str(random.choice(string.ascii_uppercase + string.digits))
         for _ in range(length)
diff --git a/moto/support/models.py b/moto/support/models.py
index 96ada0392..852e94a8c 100644
--- a/moto/support/models.py
+++ b/moto/support/models.py
@@ -4,6 +4,7 @@ from moto.moto_api._internal.managed_state_model import ManagedState
 from moto.moto_api._internal import mock_random as random
 from moto.utilities.utils import load_resource
 import datetime
+from typing import Any, Dict, List, Optional
 
 
 checks_json = "resources/describe_trusted_advisor_checks.json"
@@ -11,7 +12,7 @@ ADVISOR_CHECKS = load_resource(__name__, checks_json)
 
 
 class SupportCase(ManagedState):
-    def __init__(self, **kwargs):
+    def __init__(self, **kwargs: Any):
         # Configure ManagedState
         super().__init__(
             "support::case",
@@ -56,21 +57,21 @@ class SupportCase(ManagedState):
             }
         }
 
-    def get_datetime(self):
+    def get_datetime(self) -> str:
         return str(datetime.datetime.now().isoformat())
 
 
 class SupportBackend(BaseBackend):
-    def __init__(self, region_name, account_id):
+    def __init__(self, region_name: str, account_id: str):
         super().__init__(region_name, account_id)
-        self.check_status = {}
-        self.cases = {}
+        self.check_status: Dict[str, str] = {}
+        self.cases: Dict[str, SupportCase] = {}
 
         state_manager.register_default_transition(
             model_name="support::case", transition={"progression": "manual", "times": 1}
         )
 
-    def describe_trusted_advisor_checks(self):
+    def describe_trusted_advisor_checks(self) -> List[Dict[str, Any]]:
         """
         The Language-parameter is not yet implemented
         """
@@ -78,18 +79,17 @@ class SupportBackend(BaseBackend):
         checks = ADVISOR_CHECKS["checks"]
         return checks
 
-    def refresh_trusted_advisor_check(self, check_id):
+    def refresh_trusted_advisor_check(self, check_id: str) -> Dict[str, Any]:
         self.advance_check_status(check_id)
-        status = {
+        return {
             "status": {
                 "checkId": check_id,
                 "status": self.check_status[check_id],
                 "millisUntilNextRefreshable": 123,
             }
         }
-        return status
 
-    def advance_check_status(self, check_id):
+    def advance_check_status(self, check_id: str) -> None:
         """
         Fake an advancement through statuses on refreshing TA checks
         """
@@ -111,14 +111,13 @@ class SupportBackend(BaseBackend):
         elif self.check_status[check_id] == "abandoned":
             self.check_status[check_id] = "none"
 
-    def advance_case_status(self, case_id):
+    def advance_case_status(self, case_id: str) -> None:
         """
         Fake an advancement through case statuses
         """
-
         self.cases[case_id].advance()
 
-    def advance_case_severity_codes(self, case_id):
+    def advance_case_severity_codes(self, case_id: str) -> None:
         """
         Fake an advancement through case status severities
         """
@@ -137,28 +136,26 @@ class SupportBackend(BaseBackend):
         elif self.cases[case_id].severity_code == "critical":
             self.cases[case_id].severity_code = "low"
 
-    def resolve_case(self, case_id):
+    def resolve_case(self, case_id: str) -> Dict[str, Optional[str]]:
         self.advance_case_status(case_id)
 
-        resolved_case = {
+        return {
             "initialCaseStatus": self.cases[case_id].status,
             "finalCaseStatus": "resolved",
         }
 
-        return resolved_case
-
     # persist case details to self.cases
     def create_case(
         self,
-        subject,
-        service_code,
-        severity_code,
-        category_code,
-        communication_body,
-        cc_email_addresses,
-        language,
-        attachment_set_id,
-    ):
+        subject: str,
+        service_code: str,
+        severity_code: str,
+        category_code: str,
+        communication_body: str,
+        cc_email_addresses: List[str],
+        language: str,
+        attachment_set_id: str,
+    ) -> Dict[str, str]:
         """
         The IssueType-parameter is not yet implemented
         """
@@ -184,11 +181,11 @@ class SupportBackend(BaseBackend):
 
     def describe_cases(
         self,
-        case_id_list,
-        include_resolved_cases,
-        next_token,
-        include_communications,
-    ):
+        case_id_list: List[str],
+        include_resolved_cases: bool,
+        next_token: Optional[str],
+        include_communications: bool,
+    ) -> Dict[str, Any]:
         """
         The following parameters have not yet been implemented:
         DisplayID, AfterTime, BeforeTime, MaxResults, Language
@@ -223,10 +220,7 @@ class SupportBackend(BaseBackend):
                 continue
 
             cases.append(formatted_case)
-        case_values = {"cases": cases}
-        case_values.update({"nextToken": next_token})
-
-        return case_values
+        return {"cases": cases, "nextToken": next_token}
 
 
 support_backends = BackendDict(
diff --git a/moto/support/responses.py b/moto/support/responses.py
index a400dc36c..fc5507cfd 100644
--- a/moto/support/responses.py
+++ b/moto/support/responses.py
@@ -1,33 +1,33 @@
 from moto.core.responses import BaseResponse
-from .models import support_backends
+from .models import support_backends, SupportBackend
 import json
 
 
 class SupportResponse(BaseResponse):
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__(service_name="support")
 
     @property
-    def support_backend(self):
+    def support_backend(self) -> SupportBackend:
         return support_backends[self.current_account][self.region]
 
-    def describe_trusted_advisor_checks(self):
+    def describe_trusted_advisor_checks(self) -> str:
         checks = self.support_backend.describe_trusted_advisor_checks()
 
         return json.dumps({"checks": checks})
 
-    def refresh_trusted_advisor_check(self):
+    def refresh_trusted_advisor_check(self) -> str:
         check_id = self._get_param("checkId")
         status = self.support_backend.refresh_trusted_advisor_check(check_id=check_id)
 
         return json.dumps(status)
 
-    def resolve_case(self):
+    def resolve_case(self) -> str:
         case_id = self._get_param("caseId")
         resolve_case_response = self.support_backend.resolve_case(case_id=case_id)
         return json.dumps(resolve_case_response)
 
-    def create_case(self):
+    def create_case(self) -> str:
         subject = self._get_param("subject")
         service_code = self._get_param("serviceCode")
         severity_code = self._get_param("severityCode")
@@ -49,7 +49,7 @@ class SupportResponse(BaseResponse):
 
         return json.dumps(create_case_response)
 
-    def describe_cases(self):
+    def describe_cases(self) -> str:
         case_id_list = self._get_param("caseIdList")
         include_resolved_cases = self._get_param("includeResolvedCases", False)
         next_token = self._get_param("nextToken")
diff --git a/setup.cfg b/setup.cfg
index 7d7b3bef9..32597d466 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -239,7 +239,7 @@ disable = W,C,R,E
 enable = anomalous-backslash-in-string, arguments-renamed, dangerous-default-value, deprecated-module, function-redefined, import-self, redefined-builtin, redefined-outer-name, reimported, pointless-statement, super-with-arguments, unused-argument, unused-import, unused-variable, useless-else-on-loop, wildcard-import
 
 [mypy]
-files= moto/a*,moto/b*,moto/c*,moto/d*,moto/e*,moto/f*,moto/g*,moto/i*,moto/k*,moto/l*,moto/m*,moto/n*,moto/o*,moto/p*,moto/q*,moto/r*,moto/s3*,moto/sagemaker,moto/secretsmanager,moto/ses,moto/sqs,moto/ssm,moto/scheduler,moto/swf,moto/sns
+files= moto/a*,moto/b*,moto/c*,moto/d*,moto/e*,moto/f*,moto/g*,moto/i*,moto/k*,moto/l*,moto/m*,moto/n*,moto/o*,moto/p*,moto/q*,moto/r*,moto/s*
 show_column_numbers=True
 show_error_codes = True
 disable_error_code=abstract