[Inkscape-devel] Write SVG File ascending wise How to ?

I have add the one custom dialog in inkscape . In that i provide the on radio button that we mention the object priority

Now my svg file save like

Now i want to save svg file in ascending order , ascending operation in Priority value , After ascending svg file i want to save file like that i mention below

For that i write custom code when user select Object Path .In "sp_item_list_to_curves" function i do ascending operation in Priority value . after that i can get the Priority values in ascending order .. But when i save the file in svg format i can't get output what i want actually..!!