Add return type to client

Update function signature to include return type.

Signed-off-by: Dennis Traub <dennis.traub@gmail.com>

Author: DennisTraub

mcp_proxy_for_aws/client.py

@@ -34,7 +34,14 @@ def aws_iam_streamablehttp_client(
     sse_read_timeout: float | timedelta = 60 * 5,
     terminate_on_close: bool = True,
     httpx_client_factory: McpHttpClientFactory = create_mcp_http_client,
-):
+) -> AsyncGenerator[
+    tuple[
+        MemoryObjectReceiveStream[SessionMessage | Exception],
+        MemoryObjectSendStream[SessionMessage],
+        GetSessionIdCallback,
+    ],
+    None,
+]:
     """Create an AWS IAM-authenticated MCP streamable HTTP client.
 
     This function creates a context manager for connecting to an MCP server using AWS IAM