code: public void addInitial(G g) {
          Pair<Integer> orderAndSize = new Pair<Integer>(g.order(), g.size());
          Map<G,Integer> graphs = orderAndSizeToGraphs.get(orderAndSize);
          if (graphs == null) {
              graphs = new HashMap<G,Integer>();
              orderAndSizeToGraphs.put(orderAndSize, graphs);
              graphs.put(g, 0);
          }
          else {
              for (Map.Entry<G,Integer> e : graphs.entrySet()) {
                  if (isoTest.areIsomorphic(g, e.getKey()))
                      return;
              }
              graphs.put(g, 0);
          }
      }
docs: Fill in