private function extractInput()
    {
        $params = $this->request->getParams();
        $period = $params[self::REQ_PERIOD] ?? '';
        if (empty($period)) {
            $period = $this->hlpPeriod->getPeriodCurrent(null, 0, HPeriod::TYPE_MONTH);
        } else {
            $period = $this->hlpPeriod->normalizePeriod($period, HPeriod::TYPE_MONTH);
        }
        $dsBegin = $this->hlpPeriod->getPeriodFirstDate($period);
        $treeType = $params[self::REQ_TREE_TYPE] ?? '';
        if ($treeType != OptionTreeType::VAL_PLAIN) {
            $treeType = OptionTreeType::VAL_COMPRESS; // 'compressed' by default
        }
        return [$dsBegin, $treeType];
    }
private function extractInput()
    {
        $params = $this->request->getParams();
        $period = $params[self::REQ_PERIOD] ?? '';
        if (empty($period)) {
            $period = $this->hlpPeriod->getPeriodCurrent(null, 0, HPeriod::TYPE_MONTH);
        } else {
            $period = $this->hlpPeriod->normalizePeriod($period, HPeriod::TYPE_MONTH);
        }
        $dsBegin = $this->hlpPeriod->getPeriodFirstDate($period);
        $treeType = $params[self::REQ_TREE_TYPE] ?? '';
        if ($treeType != OptionTreeType::VAL_PLAIN) {
            $treeType = OptionTreeType::VAL_COMPRESS; // 'compressed' by default
        }
        return [$dsBegin, $treeType];
    }
Extract and validate input parameters.

@return array [$dsBegin, $treeType]