Function getbufferproc

pub unsafe fn getbufferproc(
    slf: *mut PyObject,
    buf: *mut Py_buffer,
    flags: c_int,
    f: for<'py> unsafe fn(_: Python<'py>, _: *mut PyObject, _: *mut Py_buffer, _: c_int) -> PyResult<c_int>,
) -> c_int