* adding physical_resource_id in SubnetRouteTableAssociation, Route and NatGW classes * adding tests * passing litern at test * passsing black==19.10b0 as lintern * passing test to python 2.7
* adding physical_resource_id in SubnetRouteTableAssociation, Route and NatGW classes * adding tests * passing litern at test * passsing black==19.10b0 as lintern * passing test to python 2.7