Keeping radio buttons checked when using sortable (based on http://www.ilovecolors.com.ar/preserving-radio-button-checked-state-during-drag-and-drop-jquery/)

sortables-and-radio-buttons.js

 //Based http://www.ilovecolors.com.ar/preserving-radio-button-checked-state-during-drag-and-drop-jquery/
               $('#example').sortable({ 
                   (...) 
                     start: function (e, ui) {
                                var radio_checked= {};

                                me.$el.find('input[type="radio"]', this).each(function(){
                                        if($(this).is(':checked'))
                                                radio_checked[$(this).attr('name')] = $(this).val();
                                        $(document).data('radio_checked', radio_checked);
                                });

                        }
                }).bind('sortstop', function (event, ui) {
                        var radio_restore = $(document).data('radio_checked');

                        $.each(radio_restore, function(index, value){
                                $('input[name="'+index+'"][value="'+value+'"]').prop('checked', true);
                        });
                });

What is me.$el ?