code: def _consume_single_get(response_iterator):
      
      # Calling ``list()`` consumes the entire iterator.
      all_responses = list(response_iterator)
      if len(all_responses) != 1:
          raise ValueError(
              "Unexpected response from `BatchGetDocumentsResponse`",
              all_responses,
              "Expected only one result",
          )
  
      return all_responses[0]
docs: Consume a gRPC stream that should contain a single response.
  
      The stream will correspond to a ``BatchGetDocuments`` request made
      for a single document.
  
      Args:
          response_iterator (~google.cloud.exceptions.GrpcRendezvous): A
              streaming iterator returned from a ``BatchGetDocuments``
              request.
  
      Returns:
          ~google.cloud.proto.firestore.v1beta1.\
              firestore_pb2.BatchGetDocumentsResponse: The single "get"
          response in the batch.
  
      Raises:
          ValueError: If anything other than exactly one response is returned.