Method set_mid

src/strings/tst.rs:281–283

(&mut self, x: Option<NonNull<Node<T>>>)

    }

    fn set_mid(&mut self, x: Option<NonNull<Node<T>>>) {
        self.subtries[1] = x;
    }

    fn set_right(&mut self, x: Option<NonNull<Node<T>>>) {
        self.subtries[2] = x;