code: def test_file_exists(self):
      creator = mock.Mock()
      loader = mock.Mock()
  
      # This file always does not exists as the directory is new.
      path = os.path.join(self.dir_path, "cahche")
  
      with self.assertRaises(RuntimeError):
          dataset.cache_or_load_file(path, creator, loader)
  
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 TestCacheOrLoadFileFileExists obj's underlying member method code with example usage: obj.test_file_exists() without return types