如何调整我的TableView SectionIndex

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
    let sections = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z"]
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let tableView = UITableView(frame: view.bounds, style: .plain)
        tableView.dataSource = self
        tableView.delegate = self
        view.addSubview(tableView)
        
        // 注册自定义的header视图
        tableView.register(HeaderView.self, forHeaderFooterViewReuseIdentifier: "HeaderView")
    }
    
    func numberOfSections(in tableView: UITableView) -> Int {
        return sections.count
    }
    
    func sectionIndexTitles(for tableView: UITableView) -> [String]? {
        return sections
    }
    
    func tableView(_ tableView: UITableView, sectionForSectionIndexTitle title: String, at index: Int) -> Int {
        return index
    }
    
    func tableView(_ tableView: UITableView, heightForHeaderInSection section: Int) -> CGFloat {
        return 50
    }
    
    func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
        let headerView = tableView.dequeueReusableHeaderFooterView(withIdentifier: "HeaderView") as? HeaderView
        headerView?.titleLabel.text = sections[section]
        return headerView
    }
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 10
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell") ?? UITableViewCell(style: .default, reuseIdentifier: "Cell")
        cell.textLabel?.text = "Row \(indexPath.row)"
        return cell
    }
}

class HeaderView: UITableViewHeaderFooterView {
    let titleLabel: UILabel
    
    override init(reuseIdentifier: String?) {
        titleLabel = UILabel(frame: CGRect(x: 15, y: 0, width: 200, height: 50))
        super.init(reuseIdentifier: reuseIdentifier)
        contentView.addSubview(titleLabel)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}