Nice work here. It's fun to see the project grow.

Looking through the api for b2_list_file_names , I see that one can send a prefix over to avoid getting more files back than necessary.

Often such a prefix just provides a convenience. But it looks like a prefix is necessary if your credentials don't give you access to an entire bucket.

What do you think about exposing the prefix feature in this api? One could either extend B2FileList.all or add a sister method (perhaps B2.FileList.filter?).