Turns off the light by gradually fading it out.
        The optional `duration` parameter allows for control
        of the fade out duration (in seconds)

def fade_out(self, duration=3):
        """Turns off the light by gradually fading it out.
        The optional `duration` parameter allows for control
        of the fade out duration (in seconds)"""
        super(RgbLight, self).fade_out(duration)
        self.off()