leftStringAtIndex method

@override String? leftStringAtIndex(int index)

Implementation

@override
String? leftStringAtIndex(int index) {
  if (index >= 0 && index < 12) {
    if (index == 0) {
      return digits(12, 2);
    } else {
      return digits(index, 2);
    }
  } else {
    return null;
  }
}