Function append_python_option 

pub fn append_python_option<'py, F>(
    py: Python<'py>,
    buf: &mut [u8],
    offset: usize,
    obj_option: &Option<&Py<PyAny>>,
    serde_option: &mut Option<&mut Box<dyn PyAnySerde>>,
    err: F,
) -> PyResult<usize>
where
    F: FnOnce() -> PyErr,