code: public static YearMonth of(int year, Month month) {
          Objects.requireNonNull(month, "month");
          return of(year, month.getValue());
      }
docs: Obtains an instance of {@code YearMonth} from a year and month.
  
  @param year  the year to represent, from MIN_YEAR to MAX_YEAR
  @param month  the month-of-year to represent, not null
  @return the year-month, not null
  @throws DateTimeException if the year value is invalid