CLN/STY: Nitpicks
Things I find myself doing in multiple branches
Looks fine.

Brainstorming ideas for expanding the range of what you work on: when editing a file, consider searching for TODO/FIXME comments and seeing if any of them are things you can address. (best case is right at the edge of what you're comfortable with).  E.g. there is one TODO in index.pyx that looks doable. I forgot to mention the changes I've made which are not related to styling.

@jbrockmendel @WillAyd Can you please re-review? Personally, I would stop doing such styling changes to cython (to resemble what black does) until there is black support for cython at which point we can do it in one go and consistently. > Personally, I would stop doing such styling changes to cython (to resemble what black does) until there is black support for cython at which point we can do it in one go and consistently.

Noted. thanks @MomIsBestFriend 

yeah let's hold off on cython changes for style until we have an auto formatter, however typing / fixing things are all ok.