* @volume: a #GVolume.
* @mount_operation: a #GMountOperation or %NULL to avoid user interaction.
* @cancellable: optional #GCancellable object, %NULL to ignore.
- * @callback: a #GAsyncReadyCallback.
+ * @callback: a #GAsyncReadyCallback, or %NULL.
* @user_data: a #gpointer.
*
* Mounts a volume.
* @volume: a #GVolume.
* @flags: flags affecting the unmount if required for eject
* @cancellable: optional #GCancellable object, %NULL to ignore.
- * @callback: a #GAsyncReadyCallback.
+ * @callback: a #GAsyncReadyCallback, or %NULL.
* @user_data: a #gpointer.
*
* Ejects a volume.