This is sufficiently unusual that it seems worth saying explicitly
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=35182
Reviewed-by: Will Thompson <will.thompson@collabora.co.uk>
* This function can be used to do runtime checking for types that
* might be unknown to the specific D-Bus client implementation
* version, i.e. it will return FALSE for all types this
- * implementation does not know.
+ * implementation does not know, including invalid or reserved types.
*
* @param connection the connection
* @param type the type to check