code: function(items) {
              items = $.makeArray(items);
  
              for (var i = 0; i < items.length; i++) {
                  var item = items[i];
  
                  // Make sure this element doesn't belong to another dragger
                  if ($.data(item, 'drag')) {
                      Garnish.log('Element was added to more than one dragger');
                      $.data(item, 'drag').removeItems(item);
                  }
  
                  // Add the item
                  $.data(item, 'drag', this);
  
                  // Add the listener
                  this.addListener(item, 'mousedown', '_handleMouseDown');
              }
  
              this.$items = this.$items.add(items);
          }
docs: Add Items
  
  @param {object} items Elements that should be draggable.