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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register(self, key=None, func=None, **kwargs):
 """Register a command helper function. You can register the function:: def print_help(**kwargs):
 username = kwargs.get('sender') sender = kwargs.get('receiver') return weixin.reply( username, sender=sender, content='text reply' ) weixin.register('help', print_help) It is also accessible as a decorator:: @weixin.register('help') def print_help(*args, **kwargs):
 username = kwargs.get('sender') sender = kwargs.get('receiver') return weixin.reply( username, sender=sender, content='text reply' ) """

        if func:
            if key is None:
                limitation = frozenset(kwargs.items())
                self._registry_without_key.append((func, limitation))
            else:
                self._registry[key] = func
            return func

        return self.__call__(key, **kwargs)