code: def is_py2_stdlib_module(m):
      
      if PY3:
          return False
      if not 'stdlib_path' in is_py2_stdlib_module.__dict__:
          stdlib_files = [contextlib.__file__, os.__file__, copy.__file__]
          stdlib_paths = [os.path.split(f)[0] for f in stdlib_files]
          if not len(set(stdlib_paths)) == 1:
              # This seems to happen on travis-ci.org. Very strange. We'll try to
              # ignore it.
              flog.warn('Multiple locations found for the Python standard '
                           'library: %s' % stdlib_paths)
          # Choose the first one arbitrarily
          is_py2_stdlib_module.stdlib_path = stdlib_paths[0]
  
      if m.__name__ in sys.builtin_module_names:
          return True
  
      if hasattr(m, '__file__'):
          modpath = os.path.split(m.__file__)
          if (modpath[0].startswith(is_py2_stdlib_module.stdlib_path) and
              'site-packages' not in modpath[0]):
              return True
  
      return False
docs: Tries to infer whether the module m is from the Python 2 standard library.
      This may not be reliable on all systems.