'Return the class of this sensor, from DEVICE_CLASSES.'

@property
def device_class(self):

    if (self._cameratype == 'NACamera'):
        return WELCOME_SENSOR_TYPES.get(self._sensor_name)
    elif (self._cameratype == 'NOC'):
        return PRESENCE_SENSOR_TYPES.get(self._sensor_name)
    return TAG_SENSOR_TYPES.get(self._sensor_name)
