docs: public DateTimeFormatterBuilder appendFixedDecimal(
              DateTimeFieldType fieldType, int numDigits) {
          if (fieldType == null) {
              throw new IllegalArgumentException("Field type must not be null");
          }
          if (numDigits <= 0) {
              throw new IllegalArgumentException("Illegal number of digits: " + numDigits);
          }
          return append0(new FixedNumber(fieldType, numDigits, false));
      }