code: def hybrid_forward(self, F, data, valid_length): # pylint: disable=arguments-differ
          
          # Data will have shape (T, N, C)
          if self._use_mean_pool:
              masked_encoded = F.SequenceMask(data,
                                              sequence_length=valid_length,
                                              use_sequence_length=True)
              agg_state = F.broadcast_div(F.sum(masked_encoded, axis=0),
                                          F.expand_dims(valid_length, axis=1))
          else:
              agg_state = F.SequenceLast(data,
                                         sequence_length=valid_length,
                                         use_sequence_length=True)
          return agg_state
docs: Forward logic