code: def _HasFile(self, file_name):
      
      if self._zip:
        return file_name in self._zip.namelist()
      else:
        file_path = os.path.join(self._path, file_name)
        return os.path.exists(file_path) and os.path.isfile(file_path)
docs: Returns True if there's a file in the current feed with the
         given file_name in the current feed.