How to make sapce in TabbedPage on top?

Hi, I'm trying to make space in TabbedPage on top. I created CustomTabbedPageRendererCS. But i don't know how do i coding.

public class CustomTabbedPageRenderer : TabbedPageRenderer
    {
        protected override void OnLayout(bool changed, int l, int t, int r, int b)
        {
            InvertLayoutThroughScale();
            base.OnLayout(changed, l, t, r, b);
        }

        private void InvertLayoutThroughScale()
        {

        }
    }

I want make TabbedPage like this picture. What should i use code? Thanks.