protected static Identifiable deserializeOptional(Deserializer buf) {
        byte hasObject = buf.getByte(null);
        if (hasObject == 1) {
            return create(buf);
        }
        return null;
    }
This is a convenience method to allow deserialization of an optional field. See {@link
#serializeOptional(Serializer, Identifiable)} for notes on this.

@param buf The buffer to deserialize from.
@return The instantiated object, or null.
vespajlib/src/main/java/com/yahoo/vespa/objects/Identifiable.java