examples/legacy/seq2seq/utils.py/Seq2SeqDataset/collate_fn
class Seq2SeqDataset:    def collate_fn(self, batch) -> Dict[str, torch.Tensor]:
        """Call prepare_seq2seq_batch."""
        batch_encoding: Dict[str, torch.Tensor] = self.tokenizer.prepare_seq2seq_batch(
            [x["src_texts"] for x in batch],
            tgt_texts=[x["tgt_texts"] for x in batch],
            max_length=self.max_source_length,
            max_target_length=self.max_target_length,
            return_tensors="pt",
            **self.dataset_kwargs,
        ).data
        batch_encoding["ids"] = torch.tensor([x["id"] for x in batch])
        return batch_encoding