docs: def _transition_callback(self, is_on, transition):
          """
          Callback that is called when a transition has ended.
  
          :param is_on: The on-off state to transition to.
          :param transition: The transition that has ended.
          """
          # Update state properties
          if transition.state_stages:
              state = transition.state_stages[transition.stage_index]
              if self.is_on and is_on is False:
                  # If led was turned off, set brightness to initial value
                  # so that the brightness is restored when it is turned on again
                  state['brightness'] = self.brightness
              self.set(is_on=is_on, cancel_transition=False, **state)
  
          self._active_transition = None