Fix credential package linting and type checker issues

packages/aws-credentials-http/README.md

@@ -39,9 +39,11 @@ import asyncio
 
 from aws_credentials_http import ContainerCredentialsResolver
 
+
 async def main() -> None:
     resolver = ContainerCredentialsResolver()
     identity = await resolver.get_identity(properties={})
 
+
 asyncio.run(main())
 ```

packages/aws-credentials-imds/README.md

@@ -50,9 +50,11 @@ import asyncio
 
 from aws_credentials_imds import IMDSCredentialsResolver
 
+
 async def main() -> None:
     resolver = IMDSCredentialsResolver()
     identity = await resolver.get_identity(properties={})
 
+
 asyncio.run(main())
 ```

packages/aws-credentials-sts/README.md

@@ -47,6 +47,7 @@ shared config/credentials files:
 from aws_credentials_sts import ProfileAssumeRoleCredentialsResolver
 from smithy_aws_core.config import load_config
 
+
 async def build_client() -> ServiceClient:
     return ServiceClient(
         config=ServiceClientConfig(
@@ -68,12 +69,14 @@ import asyncio
 from aws_credentials_sts import AssumeRoleCredentialsResolver
 from smithy_aws_core.identity import EnvironmentCredentialsResolver
 
+
 async def main() -> None:
     resolver = AssumeRoleCredentialsResolver(
         source_resolver=EnvironmentCredentialsResolver(),
         role_arn="arn:aws:iam::123456789012:role/example-role",
     )
     identity = await resolver.get_identity(properties={})
 
+
 asyncio.run(main())
 ```

packages/aws-credentials-sts/src/aws_credentials_sts/resolvers.py

@@ -10,6 +10,7 @@
 from importlib import metadata
 from typing import TYPE_CHECKING, cast
 
+from smithy_aws_core.config import AwsConfigOverrides
 from smithy_aws_core.config.merged_config import MergedConfig
 from smithy_aws_core.identity import (
     AWSCredentialsIdentity,
@@ -130,7 +131,7 @@ async def _assume_role(self) -> AWSCredentialsIdentity:
         from aws_sdk_sts.models import AssumeRoleInput
 
         if self._client is None:
-            overrides: dict[str, object] = {
+            overrides: AwsConfigOverrides = {
                 "aws_credentials_identity_resolver": self._source_resolver,
                 "region": self._region,
             }