// will have no isolated nodes, we can skip adding nodes explicitly and let putEdge() do it.

    if (graph.isDirected()) {
      // Note: works for both directed and undirected graphs, but we only use in the directed case.
      for (N node : graph.nodes()) {
        for (N reachableNode : reachableNodes(graph, node)) {
          transitiveClosure.putEdge(node, reachableNode);
        }
      }
    } else {

        }

        orderedNodeConnectionsBuilder.add(new NodeConnection.Pred<>(predecessor));
        predecessorCount++;
      } else { // incidentEdge is an outEdge
        checkArgument(incidentEdge.nodeU().equals(thisNode));

        N successor = incidentEdge.nodeV();
        V value = successorNodeToValueFn.apply(successor);