/// As we wish to serialize these differently from Option<T>s (Options get a tag byte, but
/// OptionalFeild simply gets Present if there are enough bytes to read into it), we have a
/// separate enum type for them.
/// As we wish to serialize these differently from Option<T>s (Options get a tag byte, but
/// OptionalFeild simply gets Present if there are enough bytes to read into it), we have a
/// separate enum type for them.