I would like to give some feedback about ...

From: https://py.checkio.org/mission/sort-by-extension/solve/

HTTP_USER_AGENT:

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.129 Safari/537.36

In the Sort by Extension mission:

assert sort_by_ext(['1.cad', '1.bat', '1.aa', '.bat']) == ['.bat', '1.aa', '1.bat', '1.cad']

It does not make sense that '.bat' is sorted to the first position. The mission clearly states that extension is the first criteria for sorting. Only when the files have the same extension then names are considered. As such, '1.aa' should come before '.bat'. Any explanation please?