fn load_greatest_key<DB: Database + ?Sized>(&mut self, db: &DB) -> Option<(LeafNode, Nibbles)> {
        let (leaf, load_result) = self.patch_set.load_greatest_key(db)?;
        self.metrics.db_reads += load_result.db_reads;
        assert_eq!(load_result.longest_prefixes.len(), 1);
        Some((leaf, load_result.longest_prefixes[0]))
    }
Loads the greatest key from the database.
core/lib/merkle_tree/src/storage/mod.rs