Nested ListView in Xamarin.Forms (ListView inside another ListView)

I have created a nested ListView in Xamarin.
But unfortunately, the binding works only with the Parent ListView and NOT with the Child List - sub ListView.

I tried to verify if there is any error with my Binding, and my binding works well with the sub List, if i make it as parent.
Any help on this binding, or approach for nested ListView bindings in Xamarin with samples would be much helpful.