i am using a bootstrap-select item in a form and i' d like to get the optgroup value for the selected value when it gets selectet, so i can evaluate what to do based on that groups value:

```
$('select.selectpicker').on('change', function(e){

        var picker_id=e.target.id;
        var selected_value = $('.selectpicker option:selected').val();
        var optgroup = ??

        switch ( optgroup){
            case "group_name":

            break

        }
});    

```

Thanks for help.