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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_transport_endpoint(self, origin, message_type, handler):
 """ Register a handler for a message received from a transport that does not indicate a message from the connected Pebble. :param origin: The type of :class:`.MessageTarget` that triggers the message :param message_type: The class of the message that is expected. :param handler: A callback to be called when a message is received. :type handler: callable :return: A handle that can be passed to :meth:`unregister_endpoint` to remove the handler. """

        return self.event_handler.register_handler((_EventType.Transport, origin, message_type), handler)