<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 async def __handle_ping(self, _ : Ping):
 """ Handle a Ping message. Pong the backend """

        self.__last_ping = time.time()
        await ZMQUtils.send(self.__backend_socket, Pong())