fix: sort iterable before passing it to itertools.groupby()

[jnussbaum]

According to the docs, the iterable must be sorted on the same key function, before passing it to itertools.groupby():
https://docs.python.org/3/library/itertools.html#itertools.groupby

[Nora-Olivia-Ammann]

It is only slightly more readable to me. To make it even better I would create a function that returns the entire iter generator.