Handle a Ping message by answering with a Pong.

def receive_ping(self, ping: Ping):
        """ Handle a Ping message by answering with a Pong. """

        self.log_healthcheck.debug(
            'Ping received',
            message_id=ping.nonce,
            message=ping,
            sender=pex(ping.sender),
        )

        pong = Pong(nonce=ping.nonce)
        self.raiden.sign(pong)

        try:
            self.maybe_send(ping.sender, pong)
        except (InvalidAddress, UnknownAddress) as e:
            self.log.debug("Couldn't send the `Delivered` message", e=e)