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)