while let Some((key, _, r)) = P::next(txn, *p, &mut cursor) {

    while let Some((key, val, r)) = P::next(txn, *p, &mut cursor) {

        writeln!(buf, "n_{}_{}[label=\"{}: {:?}\"];", p.offset, i, i, key).unwrap();

        writeln!(
            buf,
            "n_{}_{}[label=\"{}: {:?} -> {:?}\"];",
            p.offset, i, i, key, val
        )
        .unwrap();