+ * @note This interface exists to work around PHP's inheritance, so ApiMessage
+ * can extend Message and ApiRawMessage can extend RawMessage while still
+ * allowing an instanceof check for a Message object including this
+ * functionality. If for some reason you feel the need to implement this
+ * interface on some other class, that class must also implement all the
+ * public methods the Message class provides (not just those from
+ * MessageSpecifier, which as written is fairly useless).