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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 add_handler(self, handler: Handler, group: int = 0):
 """Use this method to register an update handler. You can register multiple handlers, but at most one handler within a group will be used for a single update. To handle the same update more than once, register your handler using a different group id (lower group id == higher priority). Args: handler (``Handler``):
 The handler to be registered. group (``int``, *optional*):
 The group identifier, defaults to 0. Returns: A tuple of (handler, group) """

        if isinstance(handler, DisconnectHandler):
            self.disconnect_handler = handler.callback
        else:
            self.dispatcher.add_handler(handler, group)

        return handler, group