code: def _os_listdir(self, dirname):
      f = self._lookup_mock_fs(dirname)
      if isinstance(f, dict):
          return f.keys()
      else:
          return []
  
imports: import stat
  import unittest
  import yaml
  from collections import namedtuple
  from unittest.mock import patch
  from parameterized import parameterized
  import __res
label_desc: Use image node_id 8 for calling the ImporterMocks obj's underlying member method code with example usage: obj._os_listdir(dirname) and returns: f, list