private function handleAggregators(
            ExportInterface $export, 
            QueryBuilder $qb, 
            $data, 
            array $center)
    {
        $aggregators = $this->retrieveUsedAggregators($data);
        
        foreach ($aggregators as $alias => $aggregator) {
            $formData = $data[$alias];
            $aggregator->alterQuery($qb, $formData['form']);
        }
    }