Method basename

crates/vm/src/exceptions.rs:2329–2341

(filename: &Wtf8)

        #[pymethod]
        fn __str__(zelf: &Py<PyBaseException>, vm: &VirtualMachine) -> PyResult<PyStrRef> {
            fn basename(filename: &Wtf8) -> &Wtf8 {
                let bytes = filename.as_bytes();
                let pos = if cfg!(windows) {
                    bytes.iter().rposition(|&b| b == b'/' || b == b'\\')
                } else {
                    bytes.iter().rposition(|&b| b == b'/')
                };
                match pos {
                    // SAFETY: splitting at ASCII byte boundary preserves WTF-8 validity
                    Some(pos) => unsafe { Wtf8::from_bytes_unchecked(&bytes[pos + 1..]) },
                    None => filename,
                }
            }

            let maybe_lineno = zelf
                .as_object()