MessageDeltaObject(Message delta object)

{
    "id": "string",
    "object": "thread.message.delta",
    "delta": {
        "role": "user",
        "content": [
            {
                "index": 0,
                "type": "image_file",
                "image_file": {
                    "file_id": "string",
                    "detail": "auto"
                }
            }
        ]
    }
}