code: def bulk(iterable, index=INDEX_NAME, doc_type=DOC_TYPE, action='index'):
      
      actions = compact(dict_to_op(
          to_dict(model),
          index_name=INDEX_NAME,
          doc_type=DOC_TYPE,
          op_type=action,
      ) for model in iterable)
  
      # fail fast if there are no actions
      if not actions:
          return 0
  
      items, _ = es_bulk(es_conn, actions, doc_type=doc_type, index=index)
  
      return items
docs: Wrapper of elasticsearch's bulk method
  
      Converts an interable of models to document operations and submits them to
      Elasticsearch.  Returns a count of operations when done.
  
      https://elasticsearch-py.readthedocs.io/en/master/api.html#elasticsearch.Elasticsearch.bulk
      https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-bulk.html