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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 _get_device_id(self, bus):
 """ Find the device id """

        _dbus = bus.get(SERVICE_BUS, PATH)
        devices = _dbus.devices()

        if self.device is None and self.device_id is None and len(devices) == 1:
            return devices[0]

        for id in devices:
            self._dev = bus.get(SERVICE_BUS, DEVICE_PATH + "/%s" % id)
            if self.device == self._dev.name:
                return id

        return None