code: function () {
  		var items = _.flatten(arguments);
  		for (var i = 0, l = items.length; i < l; i++) {
  			this.addItem(items[i], this.items.length);
  		}
  	}
docs: Add one or more items
  @param {*|Array.<*>} items A single item or array of items which will be
  added to this collection
  @fires add