[tiangolo]

Yep, but not secret, it's the in-progress dataclass_transform draft spec, already implemented in (open source) Pyright, and Pylance re-uses Pyright, so it gets that support.

https://github.com/microsoft/pyright/blob/main/specs/datacla...

[Xavdidtheshadow]

There you go! Not secret at all. Thanks for linking that!