validateGraph(graph);
  }

  static <N> void validateGraph(Graph<N> graph) {
    assertStronglyEquivalent(graph, Graphs.copyOf(graph));
    assertStronglyEquivalent(graph, ImmutableGraph.copyOf(graph));

    String graphString = graph.toString();
    assertThat(graphString).contains("isDirected: " + graph.isDirected());
    assertThat(graphString).contains("allowsSelfLoops: " + graph.allowsSelfLoops());

        return Ordering.natural().immutableSortedCopy(graphMap.get(node));
      }
    };
  }

  private static ImmutableGraph<Character> createSingleRootGraph() {
    MutableGraph<Character> graph = GraphBuilder.directed().build();
    graph.addNode('a');
    return ImmutableGraph.copyOf(graph);
  }

  private static void assertEqualCharNodes(Iterable<Character> result, String expectedCharacters) {

    validateGraph(graph);
  }

  static <N> void validateGraph(Graph<N> graph) {
    assertStronglyEquivalent(graph, Graphs.copyOf(graph));
    assertStronglyEquivalent(graph, ImmutableGraph.copyOf(graph));

    String graphString = graph.toString();
    assertThat(graphString).contains("isDirected: " + graph.isDirected());
    assertThat(graphString).contains("allowsSelfLoops: " + graph.allowsSelfLoops());

 * ImmutableNetwork}.
 *
 * <p>You can create an immutable copy of an existing {@code Network} using {@link
 * ImmutableNetwork#copyOf(Network)}:
 *
 * {@snippet :
 * ImmutableNetwork<Integer, MyEdge> immutableGraph = ImmutableNetwork.copyOf(network);
 * }
 *
 * <p>Instances of {@link ImmutableNetwork} do not implement {@link MutableNetwork} (obviously!) and
 * are contractually guaranteed to be unmodifiable and thread-safe.
 *