When I'm working on a function that I think I'll add more arguments to, or have a list I think I'll add more items to, I do this just so I don't have to modify

When I'm working on a function that I think I'll add more arguments to, or have a list I think I'll add more items to, I do this just so I don't have to modify the line above where I'm adding something (because I often end up forgetting the comma otherwise). It's interesting to see it pointed out that this helps with diffs.