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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 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]