code: private static void checkTransitionGroups(Map<Circuit, Collection<TileRef>> circuits,
                                                Circuit circuit,
                                                MapTile map,
                                                TileRef ref)
      {
          final MapTileGroup mapGroup = map.getFeature(MapTileGroup.class);
          final MapTileTransition mapTransition = map.getFeature(MapTileTransition.class);
          final String group = mapGroup.getGroup(ref);
          for (final String groupTransition : mapGroup.getGroups())
          {
              if (mapTransition.getTransitives(group, groupTransition).size() == 1)
              {
                  final Circuit transitiveCircuit = new Circuit(circuit.getType(), group, groupTransition);
                  getTiles(circuits, transitiveCircuit).add(ref);
              }
          }
      }
docs: Check transitions groups, and create compatible circuit on the fly.
  
  @param circuits The circuits collection.
  @param circuit The circuit found.
  @param map The map reference.
  @param ref The tile ref to add.