code: void formatISOWeekOfYear(StringBuilder b, ZonedDateTime d, int width) {
      int w = d.get(IsoFields.WEEK_OF_WEEK_BASED_YEAR);
      switch (width) {
        case 2:
          zeroPad2(b, w, 2);
          break;
          
        case 1:
          b.append(w);
          break;
      }
    }
docs: Format the week number of the year.