Tableviewcontroller does not correctly show the cells

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Apple

Xcode

Swift

Hi guys, I'm making an app with a tableview controller that I use the latest version of xcode the 9.2, and development in swift 4, then the fact is that the cells are seen in this way .
I would like to get this result: this

import UIKit

class CantieriViewController: UITableViewController {
    
    override func viewDidLoad()
    {
        super.viewDidLoad()
        
        
        self.view.backgroundColor = UIColor.white
        tableView.register(MyCell.self, forCellReuseIdentifier: "cellId")
        
    }
    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) ->Int
    {
        return 5
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) ->UITableViewCell
    {
        return tableView.dequeueReusableCell(withIdentifier: "cellId", for: indexPath as IndexPath)
    }
    
}

class MyCell: UITableViewCell {
    
    override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
        super.init(style: style, reuseIdentifier: reuseIdentifier)
        setupViews()
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    let nameLabel: UILabel = {
        let label = UILabel()
        label.text = "Sample Item"
        label.translatesAutoresizingMaskIntoConstraints = false
        label.font = UIFont.boldSystemFont(ofSize: 14)
        return label
    }()
    
    func setupViews() {
        addSubview(nameLabel)
        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": nameLabel]))
        addConstraints(NSLayoutConstraint.constraints(withVisualFormat: "V:|[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": nameLabel]))
    }
}

What I have tried:

I do not know how to solve it