fn send_signal(&self, signal: libc::c_int) -> io::Result<()> {
        let left_result = self.left_handle.send_signal(signal);
        let right_result = self.right_handle.send_signal(signal);
        left_result.and(right_result)
    }
Signals both parts of this `pipe` expression. Returns an error if signalling one of the
expressions returned an error.
src/unix.rs