this.model = new mxGraphHierarchyModel(this, vertexSet.toArray(), roots, parent);
this.model = new mxGraphHierarchyModel(this, vertexSet.toArray(), roots, parent);
this.model = new mxGraphHierarchyModel(this, vertexSet.toArray(), roots, parent);
this.model = new mxGraphHierarchyModel(this, vertexSet.toArray(), roots, parent);