Constant pyo3::ffi::Py_TPFLAGS_HAVE_VECTORCALL

pub const Py_TPFLAGS_HAVE_VECTORCALL: c_ulong = 1 << 11; // 0x0000_0000_0000_0800u64

This is supported on Py_3_8 and non-Py_LIMITED_API only.

Set if the type implements the vectorcall protocol (PEP 590)