code: def test_trust_repo_none(self):
      with warnings.catch_warnings(record=True) as w:
          warnings.simplefilter("always")
          torch.hub.load(
              "ailzhang/torchhub_example",
              "mnist_zip_1_6",
              trust_repo=None,
          )
          assert len(w) == 1
          assert issubclass(w[-1].category, UserWarning)
          assert (
              "You are about to download and run code from an untrusted repository"
              in str(w[-1].message)
          )
  
      self._assert_trusted_list_is_empty()
  
imports: import unittest
  from unittest.mock import patch
  import os
  import tempfile
  import warnings
  import torch
  import torch.hub
  from torch.testing._internal.common_utils import retry, IS_SANDCASTLE, TestCase
label_desc: Use image node_id 23 for calling the TestHub obj's underlying member method code with example usage: obj.test_trust_repo_none() without return types