It's not so hard. One of the interview stages I did somewhere well known used this.
Here's the neural net model your colleague sent you. They say it's meant to do ABC, but they found limitation XYZ. What is going on? What changes would you suggest and why?
Was actually a decent combined knowledge + code question.
There are so many interesting ways to use code reviews like subtly introducing defects and bugs and see if people can follow the logic, read the code, find where the reasoning comes up short.
I wrote up 7 general strategies for teams that are interested: https://coderev.app/blog/7-strategies-for-using-code-reviews...