Rafael,

There is already a method which returns all the extensions. What is required is a flag (or separate dict) which provides a canonical extension. The questions is whether it is sufficient to rely on the default provided mimetypes for the default in the face of mimetypes read out of the mimetypes files or windows registry.

I don't see a way to fix the bug, without also providing an API to "pick the winner" for those cases that are not provided in the default list.