docs: public static <T extends Extendable> List<T> group(final List<T> values, final Group[] groups) {
          final SortableList<T> list = getSortableList(values);
          final GroupStrategy strategy = new GroupStrategy();
          for (int i = groups.length - 1; i >= 0; i--) {
              list.sortOnProperty(groups[i], true, strategy);
          }
          return list;
      }