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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_notifications(self):
 """Start the notifications thread. If an external callback is not set up (using `update_webhook`) then calling this function is mandatory to get or set resource. .. code-block:: python Some value :returns: void """

        with self._notifications_lock:
            if self.has_active_notification_thread:
                return
            api = self._get_api(mds.NotificationsApi)
            self._notifications_thread = NotificationsThread(
                self._db,
                self._queues,
                b64decode=self.b64decode,
                notifications_api=api,
                subscription_manager=self.subscribe,
            )
            self._notifications_thread.daemon = True
            self._notifications_thread.start()