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)

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