> +0 I don't see any downside.

Thank you Raymond :)
I agree with your view, At first, I thought that instantiation time reducing is also meaningful and we already applied PEP 590 for some of the types to reduce instantiation. (e.g range(), list(), dict(), bool(), reversed(), type()..)

And also I thought that filter is one of the well-used features in Python so it was one of the candidates to apply from my sight. ;)

But if this PR only consume maintenance cost, I am okay with not to apply it doesn't matter :)

And happy new year Raymond(Sorry I am late ;) But the lunar new year was only 2weeks ago so not too late lol)