code: def should_get_id(self, action):
          
          mapping_ids = self.doc_to_get.setdefault(action["_index"], {}).setdefault(
              action["_type"], set()
          )
          if action["_id"] in mapping_ids:
              # There is an update on this id already
              return False
          else:
              mapping_ids.add(action["_id"])
              return True
docs: Mark document to retrieve its source from Elasticsearch.
          Returns:
              True - if marking document for the first time in this bulk
              False - if document has been already marked