code: func NewDigitalPin(pin int, v ...string) *DigitalPin {
  	d := &DigitalPin{pin: strconv.Itoa(pin)}
  	if len(v) > 0 {
  		d.label = v[0]
  	} else {
  		d.label = "gpio" + d.pin
  	}
  
  	return d
  }
docs: // NewDigitalPin returns a DigitalPin given the pin number and an optional sysfs pin label.
  // If no label is supplied the default label will prepend "gpio" to the pin number,
  // eg. a pin number of 10 will have a label of "gpio10"