docs: def set_state(self, state, speed=None):
          """
          :param state: bool
          :param speed: a string one of ["lowest", "low",
              "medium", "high", "auto"] defaults to last speed
          :return: nothing
          """
          speed = speed or self.current_fan_speed()
          if state:
              desired_state = {"powered": state, "mode": speed}
          else:
              desired_state = {"powered": state}
  
          response = self.api_interface.set_device_state(self, {
              "desired_state": desired_state
          })
  
          self._update_state_from_response(response)