code: def _path_isfile(self, filename):
      f = self._lookup_mock_fs(filename)
      return isinstance(f, str)
  
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 6 for calling the ImporterMocks obj's underlying member method code with example usage: obj._path_isfile(filename) and returns: isinstance