this.allowsSelfLoops = builder.allowsSelfLoops;
    this.nodeOrder = builder.nodeOrder.cast();
    // Prefer the heavier "MapRetrievalCache" for nodes if lookup is expensive.
    this.nodeConnections =
        (nodeConnections instanceof TreeMap)
            ? new MapRetrievalCache<>(nodeConnections)
            : new MapIteratorCache<>(nodeConnections);
    this.edgeCount = checkNonNegative(edgeCount);
  }

  @Override

    this.edgeOrder = builder.edgeOrder.cast();
    // Prefer the heavier "MapRetrievalCache" for nodes if lookup is expensive. This optimizes
    // methods that access the same node(s) repeatedly, such as Graphs.removeEdgesConnecting().
    this.nodeConnections =
        (nodeConnections instanceof TreeMap)
            ? new MapRetrievalCache<N, NetworkConnections<N, E>>(nodeConnections)

                  Set<Integer> unused = graph.successors(node);
                }
                /*
                 * Also look up an earlier node so that, if the graph is using MapRetrievalCache,
                 * we read one of the fields declared in that class.
                 */
                Set<Integer> unused = graph.successors(first);

                  Set<Integer> unused = graph.successors(node);
                }
                /*
                 * Also look up an earlier node so that, if the graph is using MapRetrievalCache,
                 * we read one of the fields declared in that class.
                 */
                Set<Integer> unused = graph.successors(first);