Hi,
That's not a bug per say, but I noticed a strong inconsistency in the codebase between strings with simple and double quotes.
For instance, see that line (def hist in _axes.py):

@_preprocess_data(replace_names=["x", 'weights'], label_namer="x")

I don't think there is a semantic reason for this difference between "x" and 'weights' (if there is, it's not clear).

If a maintainer thinks this should be corrected, I think a carefully designed regexp and sed command line can do the job quickly.