def fill( *args )
      closed!
      if block_given?
        @leds.fill do |ii|
          value = yield(ii)
          to_color(value)
        end
      else
        value = to_color(args.shift)
        @leds.fill(value, *args)
      end
      self
    end
def fill( *args )
      closed!
      if block_given?
        @leds.fill do |ii|
          value = yield(ii)
          to_color(value)
        end
      else
        value = to_color(args.shift)
        @leds.fill(value, *args)
      end
      self
    end
Set the selected LEDs to the given `color`. The `color` msut be given as a
 24-bit RGB value. You can also supply a block that receives an LED index and
 returns a 24-bit RGB color.

 Examples:
    leds.fill( 0x00FF00 )
    leds.fill( 0xFF0000, 2, 2 )
    leds.fill( 0x0000FF, (4...8) )
    leds.fill { |i| 256 << i }

 Returns this PixelPi::Leds instance.