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]`
return firehose_arn.split("/")[-1]
def kinesis_stream_name(kinesis_arn):
    return kinesis_arn.split(":stream/")[-1]
def mock_aws_request_headers(
    service="dynamodb", region_name=None, access_key=None, internal=False
) -> dict[str, str]:
    ctype = APPLICATION_AMZ_JSON_1_0
    if service == "kinesis":
        ctype = APPLICATION_AMZ_JSON_1_1
    elif service in ["sns", "sqs", "sts", "cloudformation"]:
        ctype = APPLICATION_X_WWW_FORM_URLENCODED
    
    
    
    access_key = access_key or get_ctx_aws_access_key_id() or TEST_AWS_ACCESS_KEY_ID
    region_name = region_name or get_region()
    headers = {
        "Content-Type": ctype,
        "Accept-Encoding": "identity",
        "X-Amz-Date": "20160623T103251Z",
        "Authorization": (
            "AWS4-HMAC-SHA256 "
            + f"Credential={access_key}/20160623/{region_name}/{service}/aws4_request, "
            + "SignedHeaders=content-type;host;x-amz-date;x-amz-target, Signature=1234"
        ),
    }
    if internal:
        headers[HEADER_LOCALSTACK_ACCOUNT_ID] = get_aws_account_id()
    return headers
def inject_region_into_auth_headers(region, headers):