code: def update(self, retry=2) -> None:
          
          try:
              _LOGGER.debug("Updating device state.")
              key = ON_KEY if not self._flip_on_off else OFF_KEY
              self.state = self._device.readCharacteristic(HANDLE) == key
          except (bluepy.btle.BTLEException, AttributeError):
              if retry < 1 or not self._connect():
                  self.available = False
                  _LOGGER.error("Failed to update device state.", exc_info=True)
                  return None
              return self.update(retry-1)
          self.available = True
          return None
docs: Synchronize state with switch.