}

    Map<Object, NodeVisitState> visitedNodes =
        Maps.newHashMapWithExpectedSize(graph.nodes().size());
    for (N node : graph.nodes()) {
      if (subgraphHasCycle(graph, visitedNodes, node)) {
        return true;
      }
    }
    return false;
  }

  /**
   * Returns true if {@code network} has at least one cycle. A cycle is defined as a non-empty