code: func (b *LEDDriver) UpLeftArrow() (err error) {
  	buf := []byte{0x1E, 0x18, 0x14, 0x12, 0x01}
  	err = b.WriteMatrix(buf)
  	return
  }
docs: // UpLeftArrow displays an arrow pointing upwards and to the left on the Microbit LEDs