def _get_special_ids(tokenizer):
    """Gets the ids of special [T] and [P] tokens."""
    trigger_token_id = tokenizer.convert_tokens_to_ids('[T]')
    if trigger_token_id == tokenizer.unk_token_id:
        raise ValueError('Tokenizer does not have special [T] token.')
    predict_token_id = tokenizer.convert_tokens_to_ids('[P]')
    if predict_token_id == tokenizer.unk_token_id:
        raise ValueError('Tokenizer does not have special [P] token.')
    return trigger_token_id, predict_token_id