public static RxTheme UseTheme <T>(this IEnumerable <T> node, RxTheme theme) where T : VisualNode
 {
     theme.Add(node.ToArray());
     return(theme);
 }
 public static RxTheme UseTheme <T>(this T node, RxTheme theme) where T : VisualNode
 {
     theme.Add(node);
     return(theme);
 }