Not a subset. It covers 100% of pure python. CPyExt are working fine , just need optimizations on some parts. The private CPyEXT calls that some libraries uses

Not a subset. It covers 100% of pure python. CPyExt are working fine , just need optimizations on some parts. The private CPyEXT calls that some libraries uses as Hacks are only things that PyPy do not support officially (PyO3 Rust-python bindings uses those) .