protected function setTHead(&$params)
    {
        $k = $this->getColumnIndex($params);

        if (isset($params['parent'])) {
            $this->theadChild[] = [
                'title' => $params['title'],
                'class' => isset($params['className']) ? $params['className'] : null,
                'colspan' => 1,
            ];
            $this->thead[$k]['colspan'] = !isset($this->thead[$k]['colspan']) ? 1 : ($this->thead[$k]['colspan']+1);
            $this->thead[$k]['title']   = $params['parent'];
            $this->header = true;
        } else {
            if (isset($params['title'])) {
                $this->thead[$k]['title']   = $params['title'];
            }
            if (isset($params['className'])) {
                $this->thead[$k]['class'] = $params['className'];
            }
        }
    }