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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_notification(self, message):
 """ add a notification in the notification queue of a user """

        sess = cherrypy.session
        username = sess.get(SESSION_KEY, None)
        if username not in self.notifications:
            self.notifications[username] = []
        self.notifications[username].append(message)