How to deal with bboxes in preprocess/augmentation layer


I want to compare the speed between augmenting images using and having the augmentation done in a preprocessing layer.
Using .map I can get to the bboxes to perform the augmentation on them also since I’m mapping the whole dataset, images, bboxes and more.
But how can I perform the augmentation on the bboxes when I’m using the preprocessing layer? Is it possible to get to the bboxes here also or does only the images go through here?