docs: def write_tarball(voevents, filepath):
      """
      Iterate over voevent models / dbrows and write to bz'd tarball.
  
      Args:
          voevents (iterable): An iterable (e.g. list) of e.g. Voevent db-rows,
              with access to the 'ivorn' and 'xml' attributes.
          filepath (string): Path to the new tarball to create. Typically of form
              '/path/to/foo.tar.bz2'
      Returns
          packet_count (int): Number of packets written to tarball
      """
      tuple_gen = ( (v.ivorn, v.xml) for v in voevents)
      return write_tarball_from_ivorn_xml_tuples(tuple_gen,
                                                 filepath)