}
    }
    /// The lowest level cause of this error — this error's cause's
    /// cause's cause etc.
    ///
    /// The root cause is the last error in the iterator produced by
    /// [`chain()`][Error::chain].
    pub fn root_cause(&self) -> &(dyn StdError + 'static) {
        let mut chain = self.chain();
        let mut root_cause = chain.next().unwrap();
        for cause in chain {
            root_cause = cause;

        root_cause