注册一个拼音风格实现

    ::

        @register('echo')
        def echo(pinyin, **kwargs):
            return pinyin

        # or
        register('echo', echo)

def register(style, func=None):
    """注册一个拼音风格实现

    ::

        @register('echo')
        def echo(pinyin, **kwargs):
            return pinyin

        # or
        register('echo', echo)
    """
    if func is not None:
        _registry[style] = func
        return

    def decorator(func):
        _registry[style] = func

        @wraps(func)
        def wrapper(pinyin, **kwargs):
            return func(pinyin, **kwargs)

        return wrapper
    return decorator