public function addRow($attribs = [], $special = self::ROW_NORMAL)
    {
        $this->rows[]['_row'] = $attribs;
        $this->activeRow = count($this->rows) - 1;

        if ($special) {
            if ($special === static::ROW_HEAD) {
                $this->specialRows['header'][] = $this->activeRow;
            } elseif ($special === static::ROW_FOOT) {
                $this->specialRows['footer'][] = $this->activeRow;
            }
        }

        return $this;
    }