code: function bustCache(stylesheet) {
          if (!stylesheet) {
            if(DEBUG) $log.error('No stylesheets provided');
            return;
          }
          var queryString = '?cache=';
          // Append query string for bust cache only once
          if (stylesheet.href.indexOf(queryString) === -1) {
            stylesheet.href = stylesheet.href + (stylesheet.bustCache ? queryString + (new Date().getTime()) : '');
          }
        }
docs: Bust Cache