code: protected SortedSet<WeekDay> getWeekDays() {
  
          SortedSet<WeekDay> result = new TreeSet<>();
          for (CmsCheckBox box : m_checkboxes) {
              if (box.isChecked()) {
                  result.add(WeekDay.valueOf(box.getInternalValue()));
              }
          }
          return result;
      }
docs: Returns all selected days.<p>
  @return all selected days