def remove(self, participant):
        """
        Unsubscribe this participant from all topic to which it is subscribed.
        """
        for topic, participants in list(self._participants_by_topic.items()):
            self.unsubscribe(participant, topic)
            # It's possible that we just nixe the last subscriber.
            if not participants:  # IE, nobody is still listening at this topic.
                del self._participants_by_topic[topic]
Unsubscribe this participant from all topic to which it is subscribed.