private function getConversionRateAggregation()
    {
        return $this->aggregationFactory->create(
            BucketInterface::TYPE_QUERY_GROUP,
            [
                'queries' => [
                    'sales' => $this->queryFactory->create(QueryInterface::TYPE_EXISTS, ['field' => 'product_sale']),
                ],
                'name' => 'conversion',
            ]
        );
    }
private function getConversionRateAggregation()
    {
        return $this->aggregationFactory->create(
            BucketInterface::TYPE_QUERY_GROUP,
            [
                'queries' => [
                    'sales' => $this->queryFactory->create(QueryInterface::TYPE_EXISTS, ['field' => 'product_sale']),
                ],
                'name' => 'conversion',
            ]
        );
    }
private function getConversionRateAggregation ( ) { return $ this -> aggregationFactory -> create ( BucketInterface :: TYPE_QUERY_GROUP , [ 'queries' => [ 'sales' => $ this -> queryFactory -> create ( QueryInterface :: TYPE_EXISTS , [ 'field' => 'product_sale' ] ) , ] , 'name' => 'conversion' , ] ) ; }
Return the child aggregation used to compute the conversion rate of sessions.

@return BucketInterface
Return the child aggregation used to compute the conversion rate of sessions .