code: def upserted_ids(self):
          
          self._raise_if_unacknowledged("upserted_ids")
          if self.__bulk_api_result:
              return dict((upsert["index"], upsert["_id"])
                          for upsert in self.bulk_api_result["upserted"])
docs: A map of operation index to the _id of the upserted document.