Thanks for the patch.  It looks good to me, but I think that adding support for Ellipsis and adding a new parameter to allow extra names are two different requests, but someone more knowledgeable than me about AST may judge differently.  My rationale is that supporting Ellipsis literals is a no-brainer addition, whereas adding an argument to support things that are not actual Python literals may be rejected.  You don’t have to split your patch in two anyway, it’s easy to do if the dev who will commit wants to.

Each change would also need a doc update.