If no arguments are specified, turn all the LEDs on. If arguments are
        specified, they must be the indexes of the LEDs you wish to turn on.
        For example::

            from gpiozero import LEDBoard

            leds = LEDBoard(2, 3, 4, 5)
            leds.on(0)    # turn on the first LED (pin 2)
            leds.on(-1)   # turn on the last LED (pin 5)
            leds.on(1, 2) # turn on the middle LEDs (pins 3 and 4)
            leds.off()    # turn off all LEDs
            leds.on()     # turn on all LEDs

        If :meth:`blink` is currently active, it will be stopped first.

        :param int args:
            The index(es) of the LED(s) to turn on. If no indexes are specified
            turn on all LEDs.

def on(self, *args):
        """
        If no arguments are specified, turn all the LEDs on. If arguments are
        specified, they must be the indexes of the LEDs you wish to turn on.
        For example::

            from gpiozero import LEDBoard

            leds = LEDBoard(2, 3, 4, 5)
            leds.on(0)    # turn on the first LED (pin 2)
            leds.on(-1)   # turn on the last LED (pin 5)
            leds.on(1, 2) # turn on the middle LEDs (pins 3 and 4)
            leds.off()    # turn off all LEDs
            leds.on()     # turn on all LEDs

        If :meth:`blink` is currently active, it will be stopped first.

        :param int args:
            The index(es) of the LED(s) to turn on. If no indexes are specified
            turn on all LEDs.
        """
        self._stop_blink()
        if args:
            for index in args:
                self[index].on()
        else:
            super(LEDBoard, self).on()