* @return a new instance of {@link EnumMap}
     * @see EnumMap#EnumMap(Class)
     */
    public static <K extends Enum<K>, V> EnumMap<K, V> newEnumMap(final Class<K> keyType) {
        return new EnumMap<>(keyType);
    }

    /**
     * Creates and returns a new instance of {@link EnumMap}.
     *
     * @param <K> the key type of {@link EnumMap}

   * associated Enum values.
   */
  @VisibleForTesting
  static <E extends Enum<E>> Map<E, LockGraphNode> createNodes(Class<E> clazz) {
    EnumMap<E, LockGraphNode> map = Maps.newEnumMap(clazz);
    E[] keys = clazz.getEnumConstants();
    int numKeys = keys.length;
    ArrayList<LockGraphNode> nodes = Lists.newArrayListWithCapacity(numKeys);
    // Create a LockGraphNode for each enum value.