return true;
    }
    return hasCycle(network.asGraph());
  }

  /**
   * Performs a traversal of the nodes reachable from {@code node}. If we ever reach a node we've
   * already visited (following only outgoing edges and without reusing edges), we know there's a
   * cycle in the graph.
   */
  private static <N> boolean subgraphHasCycle(
      Graph<N> graph,