That is at the 'edge' of your code where you are calling some function and needing to translate to your code's error type. At all the intermediate layers of fu

That is at the 'edge' of your code where you are calling some function and needing to translate to your code's error type. At all the intermediate layers of functions in languages with exceptions you write no code and just let it bubble up, while in Rust you just use `?` to send the error back up a level, while in Go you have to be verbosely explicit around every function call at every level.