* ImmutableValueGraph}.
 *
 * <p>You can create an immutable copy of an existing {@code ValueGraph} using {@link
 * ImmutableValueGraph#copyOf(ValueGraph)}:
 *
 * <pre>{@code
 * ImmutableValueGraph<Integer, Double> immutableGraph = ImmutableValueGraph.copyOf(graph);
 * }</pre>
 *
 * <p>Instances of {@link ImmutableValueGraph} do not implement {@link MutableValueGraph}

  MutableValueGraph<Integer, String> graph;

  @After
  public void validateGraphState() {
    assertStronglyEquivalent(graph, Graphs.copyOf(graph));
    assertStronglyEquivalent(graph, ImmutableValueGraph.copyOf(graph));

    Graph<Integer> asGraph = graph.asGraph();
    AbstractGraphTest.validateGraph(asGraph);
    assertThat(graph.nodes()).isEqualTo(asGraph.nodes());