swift basic grammer swift :     import UIKit

    class ViewController: UIViewController {
    @IBOutlet weak var formulalabel: UILabel!
    @IBOutlet weak var Answerlabel: UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()
        formulalabel.text = ""
        Answerlabel.text = ""
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


    @IBAction func inputformula(_ sender: Any) {
        guard let formulaText = formulalabel.text else {
            return
        }
        guard let senderedText = sender.titleLabel.text else {
            return
        }
        formulaLabel.text = formulaText + senderedText
    }
    
    @IBAction func calculationanswer(_ sender: Any) {
    }
    
    @IBAction func clearcalculation(_ sender: Any) {
    }
    }

    

I can't understand grammer in the text below .
 guard let senderedText = sender.titleLabel.text else

what is sender.titleLabel???

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