code: public boolean indexAll(Collection<G> graphs) {
          boolean modified = false;
          next_graph_to_add:
          for (G g : graphs) {
              for (Map.Entry<G,Integer> e : graphIndices.entrySet()) {
                  if (isoTest.areIsomorphic(g, e.getKey())) 
                      continue next_graph_to_add;
              }
              // No index assigned, so create a new one
              int index = graphIndices.size();
              graphIndices.put(g, index);
              modified = true;
          }
          return modified;
      }
docs: {@inheritDoc}