code: def test_cache_exists(self):
      creator = mock.Mock()
      loader = mock.Mock()
  
      file_desc, file_name = tempfile.mkstemp()
  
      try:
          dataset.cache_or_load_file(file_name, creator, loader)
      finally:
          os.close(file_desc)
          os.remove(file_name)
  
      self.assertFalse(creator.called)
      loader.assert_called_once_with(file_name)
  
imports: import os
  import shutil
  import tempfile
  import unittest
  import mock
  from chainer import dataset
  from chainer import testing
label_desc: Use image node_id 3 for calling the TestCacheOrLoadFile obj's underlying member method code with example usage: obj.test_cache_exists() without return types