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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 notifyOnDisconnect(self, callback):
 """ Registers a callback that will be called when the DBus connection underlying the remote object is lost @type callback: Callable object accepting a L{RemoteDBusObject} and L{twisted.python.failure.Failure} @param callback: Function that will be called when the connection to the DBus session is lost. Arguments are the L{RemoteDBusObject} instance and reason for the disconnect (the same value passed to L{twisted.internet.protocol.Protocol.connectionLost}) """

        if self._disconnectCBs is None:
            self._disconnectCBs = []
        self._disconnectCBs.append(callback)