public static void SaveFigures(IEnumerable <IFigure> figures, XmlWriter writer)
        {
            var serializer = new DrawingSerializer();

            serializer.WriteFigures(figures, writer);
        }
        public static void SaveDrawing(Drawing drawing, XmlWriter writer)
        {
            var serializer = new DrawingSerializer();

            serializer.Write(drawing, writer);
        }