// In a directed graph, parallel edges cannot introduce a cycle in an acyclic graph.
    // However, in an undirected graph, any parallel edge induces a cycle in the graph.
    if (!network.isDirected()
        && network.allowsParallelEdges()
        && network.edges().size() > network.asGraph().edges().size()) {
      return true;
    }
    return hasCycle(network.asGraph());
  }

  /**

    assertThat(graph.allowsSelfLoops()).isEqualTo(asNetwork.allowsSelfLoops());
    assertThat(asNetwork.edgeOrder()).isEqualTo(ElementOrder.unordered());
    assertThat(asNetwork.allowsParallelEdges()).isFalse();
    assertThat(asNetwork.asGraph()).isEqualTo(graph.asGraph());

    for (Integer node : graph.nodes()) {
      assertThat(graph.adjacentNodes(node)).isEqualTo(asGraph.adjacentNodes(node));

    assertThat(graph.allowsSelfLoops()).isEqualTo(asNetwork.allowsSelfLoops());
    assertThat(asNetwork.edgeOrder()).isEqualTo(ElementOrder.unordered());
    assertThat(asNetwork.allowsParallelEdges()).isFalse();
    assertThat(asNetwork.asGraph()).isEqualTo(graph);

    Set<EndpointPair<N>> allEndpointPairs = new HashSet<>();

    for (N node : sanityCheckSet(graph.nodes())) {

    assertThat(graph.allowsSelfLoops()).isEqualTo(asNetwork.allowsSelfLoops());
    assertThat(asNetwork.edgeOrder()).isEqualTo(ElementOrder.unordered());
    assertThat(asNetwork.allowsParallelEdges()).isFalse();
    assertThat(asNetwork.asGraph()).isEqualTo(graph.asGraph());

    for (Integer node : graph.nodes()) {
      assertThat(graph.adjacentNodes(node)).isEqualTo(asGraph.adjacentNodes(node));