fn extend_merkle_path<'a>(
        &'a self,
        path: &'a [ValueHash],
    ) -> impl Iterator<Item = ValueHash> + 'a {
        let empty_hash_count = TREE_DEPTH - path.len();
        let empty_hashes = (0..empty_hash_count).map(|depth| self.empty_subtree_hash(depth));
        empty_hashes.chain(path.iter().copied())
    }
Extends the provided `path` to length `TREE_DEPTH`.
core/lib/merkle_tree/src/hasher/mod.rs