Gather tree
gather_tree(step_ids, parent_ids, max_sequence_lengths, end_token)
| step_ids | requires the step id |
|---|---|
| parent_ids | The parent ids of shape `[max_time, batch_size, beam_width]`. |
| max_sequence_lengths | get max_sequence_length across all beams for each batch. |
| end_token | `int32` scalar, the token that marks end of decoding. |
None