code: function (items) {
          var self = this, len = self.length, i;
  
          self.length = 0;
          self.add(items);
  
          // Remove old entries
          for (i = self.length; i < len; i++) {
            delete self[i];
          }
  
          return self;
        }
docs: Sets the contents of the collection. This will remove any existing items
  and replace them with the ones specified in the input array.
  
  @method set
  @param {Array} items Array with items to set into the Collection.
  @return {tinymce.ui.Collection} Collection instance.