Uninstalling app is not removing assets added by app by Ashish Kasama

I have one app which is inserting one js file as asset using below code

"asset" => array(

                "key" => "assets/mytest.js",
                "value" => 'alert("test")';
                ));

Now I push this to each theme using 

PUT  "/admin/themes/$id/assets.json" with above data

Now stores installing app is having this asset, Now store user is adding following line in themes

{{ 'mytest.js' | asset_url | script_tag }}

but when user uninstall this app , the file mytest.js is not removed 

I read all articles which says asset added by app is deleted..

thank you