code: func (b *LEDDriver) DownRightArrow() (err error) {
  	buf := []byte{0x10, 0x09, 0x05, 0x03, 0x0F}
  	err = b.WriteMatrix(buf)
  	return
  }
docs: // DownRightArrow displays an arrow pointing down and to the right on the Microbit LEDs