 to be new parent of all regular children
          const subst = net.createVertex();
          net.addVertex(subst);
          // reparent regular children to the new substitute vertex
          eit = childedges.iterator;
          while (eit.next()) {
            const ce = eit.value;
            ce.fromVertex = subst;
            subst.addDestinationEdge(ce);
          }
          // finally can add substitute vertex as the final odd child,
          // to be positioned at the end of the PARENT's immedia