hogonal link does not cross over the assistant subtree
      const eit = this.network.edges.iterator;
      while (eit.next()) {
        const e = eit.value;
        if (e.link == null) continue;
        const r = e.link;
        // does this edge come from a substitute parent vertex?
        const subst = e.fromVertex;
        if (subst.node == null && r.routing == go.Routing.Orthogonal) {
          r.updateRoute();
          r.startRoute();
          // middle segment goes from point 2 to point 3
        