return (graph instanceof ImmutableGraph)
        ? (ImmutableGraph<N>) graph
        : new ImmutableGraph<N>(
            new StandardValueGraph<N, Presence>(
                GraphBuilder.from(graph), getNodeConnections(graph), graph.edges().size()));
  }

  /**
   * Simply returns its argument.
   *
   * @deprecated no need to use this
   */
  @Deprecated

@ElementTypesAreNonnullByDefault
public final class ImmutableValueGraph<N, V> extends StandardValueGraph<N, V> {

  private ImmutableValueGraph(ValueGraph<N, V> graph) {
    super(ValueGraphBuilder.from(graph), getNodeConnections(graph), graph.edges().size());
  }

  /** Returns an immutable copy of {@code graph}. */
  public static <N, V> ImmutableValueGraph<N, V> copyOf(ValueGraph<N, V> graph) {

@ElementTypesAreNonnullByDefault
public final class ImmutableNetwork<N, E> extends StandardNetwork<N, E> {

  private ImmutableNetwork(Network<N, E> network) {
    super(
        NetworkBuilder.from(network), getNodeConnections(network), getEdgeToReferenceNode(network));
  }

  /** Returns an immutable copy of {@code network}. */
  public static <N, E> ImmutableNetwork<N, E> copyOf(Network<N, E> network) {