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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 disconnect(self):
 """Disconnect a connected client from the broker."""

        self._state_mutex.acquire()
        self._state = mqtt_cs_disconnecting
        self._state_mutex.release()

        self._backoffCore.stopStableConnectionTimer()

        if self._sock is None and self._ssl is None:
            return MQTT_ERR_NO_CONN

        return self._send_disconnect()