protected function renderRowGroup($groups, $index, $colspan)
    {
        if ($groups && isset($groups[$index])) {
            foreach ($groups[$index] as $grow) {
                if ($this->paging) {
                    $grow[3] = "display:none;" . $grow[3];
                }
                echo "<tr from='$grow[0]' to='$grow[1]' class='row-group" . ($grow[4] ? " $grow[4]" : "") . "' " . ($grow[3] ? "style='$grow[3]'" : "") . ">";
                if (strpos($grow[2], "<td") === 0) {
                    echo $grow[2];
                } else {
                    echo "<td colspan='$colspan'>$grow[2]</td>";
                }
                echo "</tr>";
            }
        }
    }