gistfile1.js

        sortVersions: function() {
            var getLang = function (ver) { 
                    return ver.get('lang');    
                },
                getLangAndAbbr = function (ver) { 
                    return ver.get('lang') + ver.get('display_abbreviation');
                };

            this.sortedByLang = _.groupBy(this.sortBy(getLangAndAbbr), getLang);
        }