Function pallet_roles::storage::migration::storage_key_iter

pub fn storage_key_iter<K, T, H>(
    module: &[u8],
    item: &[u8]
) -> PrefixIterator<(K, T), ()> where
    K: Decode,
    T: Decode,
    H: ReversibleStorageHasher,

Construct iterator to iterate over map items in module for the map called item.