How to get top object AABB?


I am started to work with OptiX these days…

I want to ask how to get top object AABB?
I cannot find the related functions…

In this post:

They says “Being able to query the top bounding box through the API is a fair request; I’ll forward that along for consideration.”

Bust I did not find related methods to obtain Top AABB from acceleration structure…
Is there any way to get the AABB?

I want this feature too.
This makes developing a light transport algorithm shooting rays from a light source + infinite distant light (or IBL) easier.