'task_type' in iterater_input.jsonl is null

[Banner-Z]

hello, I download the datasets and write_to_jsonl, but I find all the 'task_type' in iterater_input.jsonl is null.
For example, the first line:
{"id": "iterater-test-0", "input": "In this paper, we present a new sequence-to-sequence pre-training model called ProphetNet, which introduces a novel self-supervised objective named future n-gram prediction and the proposed n-stream self-attention mechanism.", "retrieved_documents": [], "title": "", "task_type": null, "meta": []}
The other datasets are no problem. Only Iterater is. How can I solve this problem?