public Object insertVertex(Object parent,String id,Object value,double x,double y,double width,double height){
  return insertVertex(parent,id,value,x,y,width,height,null);
}

public Object insertVertex ( Object parent , String id , Object value , double x , double y , double width , double height ) { return insertVertex ( parent , id , value , x , y , width , height , null ) ; }
creates and adds a new vertex with an empty style .
