Pimcore\Model\Object\Listing::setGroupBy PHP Method

    public function setGroupBy($groupBy, $qoute = true)
    {
        $this->reset();
        if ($groupBy) {
            $this->groupBy = $groupBy;
            if (!$qoute) {
                $this->groupBy = new \Zend_Db_Expr($groupBy);
            }
        }
        return $this;
    }