Function to_bytes_from_iter 

pub fn to_bytes_from_iter<B, K, V>(
    bytes: B,
    iter: impl IntoIterator<Item = (K, V)>,
    registry_type: (&Registry, TypeId),
) -> Result<(), Error>
where
    B: BufMut + Debug,
    K: Into<String>,
    V: Into<JsonValue>,

SCALE-encode a JSON-like key-value iterator into a buffer using type info.