code: public Iterator<Node> getOrderedVersions(final Graph g, final Node subject, final Resource predicate) {
          final List<Node> vs = listObjects(g, subject, predicate.asNode()).toList();
          vs.sort(Comparator.comparing(v -> getVersionDate(g, v)));
          return vs.iterator();
      }
docs: Return an iterator of Triples for versions in order that
  they were created.
  
  @param g the graph
  @param subject the subject
  @param predicate the predicate
  @return iterator