Function sp_trie::for_keys_in_child_trie

pub fn for_keys_in_child_trie<L: TrieConfiguration, F: FnMut(&[u8]) -> bool, DB>(
    keyspace: &[u8], 
    db: &DB, 
    root_slice: &[u8], 
    f: F
) -> Result<(), Box<TrieError<L>>> where
    DB: HashDBRef<L::Hash, DBValue>, 

Call f for all keys in a child trie. Aborts as soon as f returns false.