fix: test_prepend_prompt_with_mixed_variables mock (#4979)

Author: mattf

tests/unit/providers/agents/meta_reference/test_openai_responses.py

@@ -1687,15 +1687,17 @@ async def test_prepend_prompt_with_mixed_variables(openai_responses_impl, mock_p
     mock_image_content = b"fake_image_data"
     mock_file_content = b"fake_doc_content"
 
-    async def mock_retrieve_file_content(file_id):
+    async def mock_retrieve_file_content(request):
+        file_id = request.file_id
         if file_id == "file-photo-123":
             return type("obj", (object,), {"body": mock_image_content})()
         elif file_id == "file-doc-456":
             return type("obj", (object,), {"body": mock_file_content})()
 
     mock_files_api.openai_retrieve_file_content.side_effect = mock_retrieve_file_content
 
-    def mock_retrieve_file(file_id):
+    def mock_retrieve_file(request):
+        file_id = request.file_id
         if file_id == "file-photo-123":
             return OpenAIFileObject(
                 object="file",