code: def get_zonefile_instance(new_instance=False):
      
      if new_instance:
          zif = None
      else:
          zif = getattr(get_zonefile_instance, '_cached_instance', None)
  
      if zif is None:
          zif = ZoneInfoFile(getzoneinfofile_stream())
  
          get_zonefile_instance._cached_instance = zif
  
      return zif
docs: This is a convenience function which provides a :class:`ZoneInfoFile`
      instance using the data provided by the ``dateutil`` package. By default, it
      caches a single instance of the ZoneInfoFile object and returns that.
  
      :param new_instance:
          If ``True``, a new instance of :class:`ZoneInfoFile` is instantiated and
          used as the cached instance for the next call. Otherwise, new instances
          are created only as necessary.
  
      :return:
          Returns a :class:`ZoneInfoFile` object.
  
      .. versionadded:: 2.6