code: public Collection<Location> orderedLocations() {
          TreeSet<Location> tree = new TreeSet<>();
          for (Iterator<Location> locs = locationIterator(); locs.hasNext();) {
              Location loc = locs.next();
              tree.add(loc);
          }
          return tree;
      }
docs: Returns a collection of locations, ordered according to the compareTo
  ordering over locations. If you want to list all the locations in a CFG
  for debugging purposes, this is a good order to do so in.
  
  @return collection of locations