def METHOD_NAME(data_ds):
    """
    Insert idioms into positions of `#idiom#` so that the task is converted
    to binary classification.
    """
    split_data_ds = []
    for example in data_ds:
        fragments = example["content"].split("#idiom#")
        label = example.get("answer", None)
        for index, cand in enumerate(example["candidates"]):
            new_example = {"content_pre": fragments[0], "content_post": fragments[1], "idiom": cand}
            if label is not None:
                new_example["label"] = str(int(index == label))
            split_data_ds.append(new_example)
    return MapDataset(split_data_ds)