code: function (prop, fn) {
        if (typeof prop === 'function') {
          fn = prop;
          prop = undefined;
        }
  
        if (typeof prop === 'undefined') {
          return this.sortByKeys(fn);
        }
        return this.sortByItems(prop, fn);
      }
docs: Sort list items.
  
  @param  {String} `prop` Property to sort by, undefined to sort by keys.
  @param  {Function} `fn` Optional getter function to get items by.
  @return {Object} Returns current instance to enable chaining
  @api public