public function update_row_group(Frame $group, Frame $last_row)
    {
        $g_key = $group->get_id();
        $r_key = $last_row->get_id();

        $r_rows = $this->_frames[$g_key]["rows"];
        $this->_frames[$g_key]["rows"] = range($this->_frames[$g_key]["rows"][0], end($r_rows));
    }