t) Object.assign(this, init);
    }

    static _cachedLinks = [];

    createNetwork() {
      return new VirtualizedTreeNetwork(this); // defined below
    }

    // ignore the argument, an (implicit) collection of Parts
    makeNetwork(coll) {
      const net = this.createNetwork();
      net.addData(this.model); // use the model data, not any actual Nodes and Links
      return net;
    }

    commitLayout() {
      VirtualizedTreeEdge._dummyLink = this.diagram.linkTemplate.copy();
      VirtualizedTree