assertThat(networkString).contains("isDirected: " + network.isDirected());
    assertThat(networkString).contains("allowsParallelEdges: " + network.allowsParallelEdges());
    assertThat(networkString).contains("allowsSelfLoops: " + network.allowsSelfLoops());

    int nodeStart = networkString.indexOf("nodes:");
    int edgeStart = networkString.indexOf("edges:");
    String nodeString = networkString.substring(nodeStart, edgeStart);

   * Attempting to add a self-loop to a network that does not allow them will throw an {@link
   * IllegalArgumentException}.
   */
  boolean allowsSelfLoops();

  /** Returns the order of iteration for the elements of {@link #nodes()}. */
  ElementOrder<N> nodeOrder();

  /** Returns the order of iteration for the elements of {@link #edges()}. */

  public static <N> ImmutableGraph<N> transitiveClosure(Graph<N> graph) {
    ImmutableGraph.Builder<N> transitiveClosure =
        GraphBuilder.from(graph).allowsSelfLoops(true).<N>immutable();
    // Every node is, at a minimum, reachable from itself. Since the resulting transitive closure
    // will have no isolated nodes, we can skip adding nodes explicitly and let putEdge() do it.

  public static <N> ImmutableGraph<N> transitiveClosure(Graph<N> graph) {
    ImmutableGraph.Builder<N> transitiveClosure =
        GraphBuilder.from(graph).allowsSelfLoops(true).<N>immutable();
    // Every node is, at a minimum, reachable from itself. Since the resulting transitive closure
    // will have no isolated nodes, we can skip adding nodes explicitly and let putEdge() do it.