def preprocess_sentence(start_sign, end_sign, sentence):
    """
    用于给句子首尾添加start和end
    Args:
        start_sign: 开始标记
        end_sign: 结束标记
        sentence: 处理的语句
    Returns:
        合成之后的句子
    """
    sentence = start_sign + ' ' + sentence + ' ' + end_sign
    return sentence