}
impl Untracked {
    fn check_last_error(&mut self) -> Result<(), std::io::Error> {
        if let Some(j) = self.join.take() {
            return j.join().expect("iterator thread panicked");
        }
        Ok(())
    }
}
impl Drop for Untracked {
    fn drop(&mut self) {
        let _ = self.check_last_error();
    }

            if let Some(j) = self.join.take() {
                if let Ok(Err(e)) = j.join() {
                    return Some(Err(e));
                }

            if let Err(e) = self.check_last_error() {
                return Some(Err(e));