docs: def readdir(self, path, fh):
          """Called by FUSE when a directory is opened.
  
          Returns a list of file and directory names for the directory.
  
          """
          log.debug('readdir(): {}'.format(path))
          try:
              dir = self._directory_cache[path]
          except KeyError:
              dir = self._get_directory(path)
              self._directory_cache[path] = dir
          return dir