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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 unsubscribe(self, connection, destination):
 """ Unsubscribes a connection from the specified topic destination. @param connection: The client connection to unsubscribe. @type connection: L{coilmq.server.StompConnection} @param destination: The topic destination (e.g. '/topic/foo') @type destination: C{str} """

        self.log.debug("Unsubscribing %s from %s" % (connection, destination))
        if connection in self._topics[destination]:
            self._topics[destination].remove(connection)

        if not self._topics[destination]:
            del self._topics[destination]