https://bugzilla.gnome.org/show_bug.cgi?id=752656
* all object paths
* @arg0: (allow-none): contents of first string argument to match on or %NULL
* to match on all kinds of arguments
- * @flags: flags describing how to subscribe to the signal (currently unused)
+ * @flags: #GDBusSignalFlags describing how arg0 is used in subscribing to the
+ * signal
* @callback: callback to invoke when there is a signal matching the requested data
* @user_data: user data to pass to @callback
* @user_data_free_func: (allow-none): function to free @user_data with when