UITableViewCell中.如何以编程方式将textLabel对齐到顶部？

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
    cell.textLabel?.text = "这是一个示例文本"
    cell.textLabel?.frame = CGRect(x: 0, y: 0, width: cell.bounds.width, height: cell.bounds.height)
    cell.textLabel?.autoresizingMask = [.flexibleWidth, .flexibleHeight]
    return cell
}