还原原始的韵母

def convert_finals(pinyin):
    """还原原始的韵母"""
    pinyin = convert_zero_consonant(pinyin)
    pinyin = convert_uv(pinyin)
    pinyin = convert_iou(pinyin)
    pinyin = convert_uei(pinyin)
    pinyin = convert_uen(pinyin)
    return pinyin