lockGraphNodesPerType = new MapMaker().weakKeys().makeMap();

  /** Creates a {@code CycleDetectingLockFactory.WithExplicitOrdering<E>}. */
  public static <E extends Enum<E>> WithExplicitOrdering<E> newInstanceWithExplicitOrdering(
      Class<E> enumClass, Policy policy) {
    // createNodes maps each enumClass to a Map with the corresponding enum key
    // type.