docs: protected int[] mergePeriodInto(int[] values, ReadablePeriod period) {
          for (int i = 0, isize = period.size(); i < isize; i++) {
              DurationFieldType type = period.getFieldType(i);
              int value = period.getValue(i);
              checkAndUpdate(type, values, value);
          }
          return values;
      }