Hi @yusukemori
We are in the process of re-writing the seq2seq fine-tuning scripts, and Seq2SeqDataCollator will probably be deprecated, so I would wait to adapt the code to the latest version, you could check out this PR, if you want to try the new script New run_seq2seq script by sgugger · Pull Request #9605 · huggingface/transformers · GitHub 25