https://github.com/localstack/localstack/blob/e7efc768a20e75feafe3702a5a6e477a233feff2/localstack/utils/aws/aws_stack.py#L904

```
File "/usr/local/lib/python3.8/site-packages/localstack/services/generic_proxy.py", line 50, in <module>
from localstack.utils.aws import aws_stack
File "/usr/local/lib/python3.8/site-packages/localstack/utils/aws/aws_stack.py", line 904, in <module>
) -> dict[str, str]:
TypeError: 'type' object is not subscriptable
```

Please fix to `Dict[str, str]`
"""Check whether a valid region is provided, and if not then raise an Exception."""
    auth_header = headers.get("Authorization")
    if not auth_header:
        raise Exception('Unable to find "Authorization" header in request')
    replaced = re.sub(r".*Credential=([^,]+),.*", r"\1", auth_header)
    if auth_header == replaced:
        raise Exception('Unable to find "Credential" section in "Authorization" header')
    
    
    parts = replaced.split("/")
    region = parts[2]
    if region not in get_valid_regions():
        raise Exception(f'Invalid region specified in "Authorization" header: "{region}"')
def set_default_region_in_headers(headers, service=None, region=None):
    
    
    if not config.USE_SINGLE_REGION:
        return
    auth_header = headers.get("Authorization")
    region = region or get_region()
    if not auth_header:
        if service:
            headers["Authorization"] = mock_aws_request_headers(service, region_name=region)[
                "Authorization"
            ]
        return
    replaced = re.sub(r"(.*Credential=[^/]+/[^/]+/)([^/])+/", r"\1%s/" % region, auth_header)
    headers["Authorization"] = replaced
def fix_account_id_in_arns(response, colon_delimiter=":", existing=None, replace=None):