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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 start_health_check(self, recipient):
 """ Starts a task for healthchecking `recipient` if there is not one yet. It also whitelists the address """

        if recipient not in self.addresses_events:
            self.whitelist(recipient)  # noop for now, for compatibility
            ping_nonce = self.nodeaddresses_to_nonces.setdefault(
                recipient,
                {'nonce': 0},  # HACK: Allows the task to mutate the object
            )

            events = healthcheck.HealthEvents(
                event_healthy=Event(),
                event_unhealthy=Event(),
            )

            self.addresses_events[recipient] = events

            greenlet_healthcheck = gevent.spawn(
                healthcheck.healthcheck,
                self,
                recipient,
                self.event_stop,
                events.event_healthy,
                events.event_unhealthy,
                self.nat_keepalive_retries,
                self.nat_keepalive_timeout,
                self.nat_invitation_timeout,
                ping_nonce,
            )
            greenlet_healthcheck.name = f'Healthcheck for {pex(recipient)}'
            greenlet_healthcheck.link_exception(self.on_error)
            self.greenlets.append(greenlet_healthcheck)