code: def _del_all_subscriptions(self, session):
          
          filter_queue = deque()
          for topic in self._subscriptions:
              if self._del_subscription(topic, session):
                  filter_queue.append(topic)
          for topic in filter_queue:
              if not self._subscriptions[topic]:
                  del self._subscriptions[topic]
docs: Delete all topic subscriptions for a given session
          :param session:
          :return: