pub fn empty_tree_hash() -> H256 {
        let hasher = P::Hasher::default();
        let min_guard_hash = hasher.hash_leaf(&Leaf::MIN_GUARD);
        let max_guard_hash = hasher.hash_leaf(&Leaf::MAX_GUARD);
        let mut hash = hasher.hash_branch(&min_guard_hash, &max_guard_hash);
        for depth in 1..P::TREE_DEPTH {
            hash = hasher.hash_branch(&hash, &hasher.empty_subtree_hash(depth));
        }
        hash
    }
Returns the hash of the empty tree.
core/lib/zk_os_merkle_tree/src/lib.rs