move_before
Description:
Moves iter in this to the position before position.
Note:
Use [class@Gtk.TreeListModel] instead
iter and position should be in the same level.
Note that this function only works with unsorted stores.
If position is null, iter will be moved to the end of the level.
Parameters:
| this |
A `GtkTreeStore` |
| iter |
A `GtkTreeIter` |
| position |
A `GtkTreeIter` |