I don't understand what I should return: a string? a list of strings? nothing?

Hi, I am currently on the arithmetic_arranger problem. To be honest, I didn’t want to look at the starter code so I wrote everything from scratch on VScode. I found a solution and everything looked good.
However, when I went to the replit link. I was surprised to find I should return arranged_problems? the way I understood the task: I get a list of strings of operations and I print them a certain way as in: my solution has no return value.
So now I am confused what are arranged_problems? a list of strings where the strings are the lines? or a string of a dictionaries where each dictionary is compromised of the lines of the operation vertically?

Your code so far

Challenge: Arithmetic Formatter

Link to the challenge:

You should return a single string from your function. You shouldn’t print anything.