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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(self):
 """Start the subscriber. """

        def _get_addr_loop(service, timeout):
            """Try to get the address of *service* until for *timeout* seconds.
            """
            then = datetime.now() + timedelta(seconds=timeout)
            while datetime.now() < then:
                addrs = get_pub_address(service, nameserver=self._nameserver)
                if addrs:
                    return [addr["URI"] for addr in addrs]
                time.sleep(1)
            return []

        # Subscribe to those services and topics.
        LOGGER.debug("Subscribing to topics %s", str(self._topics))
        self._subscriber = Subscriber(self._addresses,
                                      self._topics,
                                      translate=self._translate)

        if self._addr_listener:
            self._addr_listener = _AddressListener(self._subscriber,
                                                   self._services,
                                                   nameserver=self._nameserver)

        # Search for addresses corresponding to service.
        for service in self._services:
            addresses = _get_addr_loop(service, self._timeout)
            if not addresses:
                LOGGER.warning("Can't get any address for %s", service)
                continue
            else:
                LOGGER.debug("Got address for %s: %s",
                             str(service), str(addresses))
            for addr in addresses:
                self._subscriber.add(addr)

        return self._subscriber