ARFoundation 2.2 : taking a screenshot of the model with the realworld picture

hi guys,
i cannot manage to actually take a snapshot from the real AR camera feed.
i tried to use a render texture from a second camera, and it only captures the virtual items without the real world.
then i saw there is ARCameraBackground class and i assume it has something to do with this, but i cant find any example of the Blit command.

i am using AR Foundation vs 2.2.0 preview 6

is there a chance you could explain me how to get a texture from the camera feed frame?

 

Please refer to the Accessing the Camera Image on the CPU documentation.