docs: public YearMonthDay withFieldAdded(DurationFieldType fieldType, int amount) {
          int index = indexOfSupported(fieldType);
          if (amount == 0) {
              return this;
          }
          int[] newValues = getValues();
          newValues = getField(index).add(this, index, newValues, amount);
          return new YearMonthDay(this, newValues);
      }