I disagree, I think returns should either be at the very start (checking inputs should be able to return before anything happens based on invalid inputs) or at the very end. Proceeding to do a bunch of stuff & then try to undo it because an input was invalid is error-prone.
If the input parameters are invalid there is an error in the program so it makes more sense to use the assert function. Why would you need to undo something due to the restriction of a single point of exit?
