public function setCountOnly(
        \DateTime $dateFrom,
        \DateTime $dateTo,
        $groupUnit = '',
        ChartQuery $chartQuery = null
    ) {
        $this->countOnly  = true;
        $this->dateFrom   = $dateFrom;
        $this->dateTo     = $dateTo;
        $this->groupUnit  = $groupUnit;
        $this->chartQuery = $chartQuery;
    }