extractOne, scorer = partial_ratio, and string capitalization

[wessonmo]

When I execute an extractOne like process.extractOne('ab', ['ab wertyu'], scorer = fuzz.partial_ratio), the result is: ('ab wertyu', 100).

However, when I take the same strings and capitalize some letters process.extractOne('AB', ['AB wertyu'], scorer = fuzz.partial_ratio), I get: ('AB wertyu', 0).

The problem only seems to be with extractOne because when I use fuzz.partial_ratio('AB', 'AB wertyu'), the result is: 100.

Is there just something I don't understand about the way extractOne works or is this an issue?