code: def on(self, *args):
          
          self._stop_blink()
          if args:
              for index in args:
                  self[index].on()
          else:
              super(LEDBoard, self).on()
docs: 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.