code: public <S extends SortedGrouping<?>> void add(int id, S set) {
  		cacheSetType(id, SetType.SORTED_GROUPING);
  		sortedGroupings.put(id, set);
  	}
docs: Adds the given {@link SortedGrouping} to this cache for the given ID.
  
  @param id  Set ID
  @param set SortedGrouping to add
  @param <S> SortedGrouping class