code: public Set<SortedSet<T>> allSets() {
          final List<UBNode<T>> allEndOfPathNodes = getAllEndOfPathNodes(this.rootNodes);
          final Set<SortedSet<T>> allSets = new LinkedHashSet<>();
          for (UBNode<T> endOfPathNode : allEndOfPathNodes) {
              allSets.add(endOfPathNode.set());
          }
          return allSets;
      }
docs: Returns all sets in this UBTree.
  @return all sets in this UBTree