Transition wrapper.

        Short-circuit transition if necessary.

        :param duration: Duration of transition.
        :param brightness: Transition to this brightness.
        :param temperature: Transition to this temperature.

def transition(self, duration, brightness=None, temperature=None):
        """ Transition wrapper.

        Short-circuit transition if necessary.

        :param duration: Duration of transition.
        :param brightness: Transition to this brightness.
        :param temperature: Transition to this temperature.
        """
        # Transition immediately if duration is zero.
        if duration == 0:
            if brightness is not None:
                self.brightness = brightness
            if temperature is not None:
                self.temperature = temperature
            return
        if brightness != self.brightness or temperature != self.temperature:
            self._transition(duration, brightness, temperature)