def METHOD_NAME(w: Writer, msg: StellarManageDataOp) -> None:
    if len(msg.key) > 64:
        raise ProcessError("Stellar: max length of a key is 64 bytes")
    write_string(w, msg.key)
    write_bool(w, bool(msg.value))
    if msg.value:
        write_string(w, msg.value)