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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 add_listener(self, listener):
 """Register a listener that will be notified of incoming messages and errors. :type listener: :class:`SessionListener` """

        self.logger.debug('installing listener %r', listener)
        if not isinstance(listener, SessionListener):
            raise SessionError("Listener must be a SessionListener type")
        with self._lock:
            self._listeners.add(listener)