Set the group saturation.

        :param saturation: Saturation in decimal percent (0.0-1.0).

def saturation(self, saturation):
        """ Set the group saturation.

        :param saturation: Saturation in decimal percent (0.0-1.0).
        """
        if saturation < 0 or saturation > 1:
            raise ValueError("Saturation must be a percentage "
                             "represented as decimal 0-1.0")
        self._saturation = saturation
        self._update_color()
        if saturation == 0:
            self.white()
        else:
            cmd = self.command_set.saturation(saturation)
            self.send(cmd)