code: @SuppressWarnings("unchecked")
  	public <T> SortedGrouping<T> getSortedGrouping(int id) {
  		return verifyType(id, sortedGroupings.get(id), SetType.SORTED_GROUPING);
  	}
docs: Returns the cached {@link SortedGrouping} for the given ID.
  
  @param id  Set ID
  @param <T> SortedGrouping type
  @return Cached SortedGrouping
  @throws IllegalStateException if the cached set is not a SortedGrouping