code: def onion_study(in_conn, out_conn, data_source):
      
      onion = OnionStudy(in_connector=in_conn, out_connector=out_conn, data_source=data_source)
      ndocs = onion.analyze()
      return ndocs
docs: Build and index for onion from a given Git index.
  
      :param in_conn: ESPandasConnector to read from.
      :param out_conn: ESPandasConnector to write to.
      :param data_source: name of the date source to generate onion from.
      :return: number of documents written in ElasticSearch enriched index.