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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 cancelSignalNotification(self, rule_id):
 """ Cancels a callback previously registered with notifyOnSignal """

        if self._signalRules and rule_id in self._signalRules:
            self.objHandler.conn.delMatch(rule_id)
            self._signalRules.remove(rule_id)