Set the brightness.

        :param brightness: Value to set (0.0-1.0).

def brightness(self, brightness):
        """ Set the brightness.

        :param brightness: Value to set (0.0-1.0).
        """
        try:
            cmd = self.command_set.brightness(brightness)
            self.send(cmd)
            self._brightness = brightness
        except AttributeError:
            self._setter('_brightness', brightness,
                         self._dimmest, self._brightest,
                         self._to_brightness)