把带声调字符替换为没有声调的字符

def replace_symbol_to_no_symbol(pinyin):
    """把带声调字符替换为没有声调的字符"""
    def _replace(match):
        symbol = match.group(0)  # 带声调的字符
        # 去掉声调: a1 -> a
        return RE_NUMBER.sub(r'', PHONETIC_SYMBOL_DICT[symbol])

    # 替换拼音中的带声调字符
    return RE_PHONETIC_SYMBOL.sub(_replace, pinyin)