public static void AddShape(this GroupShapeViewModel group, BaseShapeViewModel shape)
{
shape.Owner = group;
shape.State &= ~ShapeStateFlags.Standalone;
group.Shapes = group.Shapes.Add(shape);
}
public static void Group(this GroupShapeViewModel group, IEnumerable <BaseShapeViewModel> shapes, IList <BaseShapeViewModel> source = null)
{
if (shapes is { })
