chart.othersGrouper(function (topItems, restItems) {
   var restItemsSum = d3.sum(restItems, _chart.valueAccessor()),
   restKeys = restItems.map(_chart.keyAccessor());
   
   if (restItemsSum > 0) {
      return topItems.concat([{
         others: restKeys,
         key: _chart.othersLabel(),
         value: restItemsSum
      }]);
   }
   return topItems;
});