code: function(){
          var sorters = this.sorters.items,
              len = sorters.length,
              i = 0,
              sorter;
              
          for (; i < len; ++i) {
              sorter = sorters[i];
              if (!sorter.isGrouper) {
                  return sorter;    
              }
          }
          return null;
      }
docs: Gets the first sorter from the sorters collection, excluding
  any groupers that may be in place
  @protected
  @return {Ext.util.Sorter} The sorter, null if none exist