> maybe it was a mistake to expose this

I was wondering if this was accidentally added at the time too.

> Remind me what use is made of this from C code

It's required for a C extension type to implement the __class_getitem__ method properly. Eg. ``MyCType[int]``. The other alternative is for them to import the types.GenericAlias Python constructor and call that, but that seems strange.

> Can we remove this from the stable API during beta? It was never exposed before.

Unfortunately, it seems like it has been (accidentally?) exposed since 3.9 :(. I see some 3rd party projects using it already, so I don't know if we can get rid of it so easily:
https://github.com/Nuitka/Nuitka/blob/57fecfe6cc939f4694b57d2efa37d1893c06b85b/nuitka/build/include/nuitka/helper/subscripts.h#L97

CC-ing Petr, seeking advice on the C stable ABI for this please.