code: def set_dimmer(self, dimmer, *, index=0, transition_time=None):
          
          self._value_validate(dimmer, RANGE_BRIGHTNESS, "Dimmer")
  
          values = {
              ATTR_LIGHT_DIMMER: dimmer
          }
  
          if transition_time is not None:
              values[ATTR_TRANSITION_TIME] = transition_time
  
          return self.set_values(values, index=index)
docs: Set dimmer value of a light.
          transition_time: Integer representing tenth of a second (default None)