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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 update_or_expire_session(self):
 """ Deletes session if keepalive request expired otherwise updates the keepalive timestamp value """

        if not hasattr(self, 'key'):
            return
        now = time.time()
        timestamp = float(self.get() or 0) or now
        sess_id = self.sess_id or UserSessionID(self.user_id).get()
        if sess_id and now - timestamp > self.SESSION_EXPIRE_TIME:
            Session(sess_id).delete()
            return False
        else:
            self.set(now)
            return True