code: private Circuit getCircuitOverTransition(Circuit circuit, Tile neighbor)
      {
          final String group = getTransitiveGroup(circuit, neighbor);
          final Circuit newCircuit;
          if (TileGroupType.TRANSITION == mapGroup.getType(circuit.getIn()))
          {
              newCircuit = new Circuit(circuit.getType(), group, circuit.getOut());
          }
          else if (TileGroupType.TRANSITION == mapGroup.getType(circuit.getOut()))
          {
              newCircuit = new Circuit(circuit.getType(), circuit.getIn(), group);
          }
          else
          {
              newCircuit = circuit;
          }
          return newCircuit;
      }
docs: Get the circuit, supporting over existing transition.
  
  @param circuit The initial circuit.
  @param neighbor The neighbor tile which can be a transition.
  @return The new circuit or original one.