Function sp_trie::child_delta_trie_root

pub fn child_delta_trie_root<L: TrieConfiguration, I, A, B, DB, RD, V>(
    keyspace: &[u8], 
    db: &mut DB, 
    root_data: RD, 
    delta: I
) -> Result<<L::Hash as Hasher>::Out, Box<TrieError<L>>> where
    I: IntoIterator<Item = (A, B)>,
    A: Borrow<[u8]>,
    B: Borrow<Option<V>>,
    V: Borrow<[u8]>,
    RD: AsRef<[u8]>,
    DB: HashDB<L::Hash, DBValue>, 

Determine a child trie root given a hash DB and delta values. H is the default hasher, but a generic implementation may ignore this type parameter and use other hashers.