How can I use Xamarin.Forms.Platform.UWP.TabbedPageRenderer ? No method to override!

I am trying to create a renderer for a tabbed page. When I look at TabbedPageRenderer, there is nothing to override :

`namespace Xamarin.Forms.Platform.UWP
{
public class TabbedPageRenderer : IVisualElementRenderer, IRegisterable, IDisposable, ITitleProvider
{
public TabbedPageRenderer();

    public FrameworkElement ContainerElement { get; }
    public Pivot Control { get; }
    public TabbedPage Element { get; }
    protected VisualElementTracker<Page, Pivot> Tracker { get; set; }

    public event EventHandler<VisualElementChangedEventArgs> ElementChanged;

    public void Dispose();
    public SizeRequest GetDesiredSize(double widthConstraint, double heightConstraint);
    public void SetElement(VisualElement element);
    protected virtual void Dispose(bool disposing);
    protected void OnElementChanged(VisualElementChangedEventArgs e);
}

}`

The usual method gives an error:

public class CustomTabRenderer : TabbedPageRenderer
        {
            protected override void OnElementChanged(VisualElementChangedEventArgs e)
            {
                base.OnElementChanged(e);
            }
        }

what can I do here?