Function cast_optional_function_argument 

pub unsafe fn cast_optional_function_argument<'py>(
    py: Python<'py>,
    raw_arg: *mut PyObject,
) -> Option<Borrowed<'py, 'py, PyAny>>

As above, but for optional arguments which may be NULL.

Safety

• raw_arg must be a valid *mut ffi::PyObject for the lifetime 'py, or NULL.