code: def test_method_retrieve(self, client: OpenAI) -> None:
      file = client.beta.assistants.files.retrieve(
          "string",
          assistant_id="string",
      )
      assert_matches_type(AssistantFile, file, path=["response"])
  
imports: from __future__ import annotations
  import os
  from typing import Any, cast
  import pytest
  from openai import OpenAI, AsyncOpenAI
  from tests.utils import assert_matches_type
  from openai._client import OpenAI, AsyncOpenAI
  from openai.pagination import SyncCursorPage, AsyncCursorPage
  from openai.types.beta.assistants import AssistantFile, FileDeleteResponse
label_desc: Use image node_id 5 for calling the TestFiles obj's underlying member method code with example usage: obj.test_method_retrieve(client) without return types