Why do you animate with the keyboard even though you didn't write the animation process?

import UIKit

classViewController:UIViewController, UITextViewDelegate{
    @IBOutlet weak var hogeTextView: UITextView!

    override func viewDidLoad(){
        super.viewDidLoad()

        self.hogeTextView.delegate=self

        NotificationCenter.default.addObserver(self,selector:#selector(keyboardWillChange), name:UIResponder.keyboardWillChangeFrameNotification, object:nil)
        NotificationCenter.default.addObserver(self,selector:#selector(keyboardWillHide),name:UIResponder.keyboardWillHideNotification,object:nil)
    }

    @objc func keyboardWillChange (notification:NSNotification) {
        guardlet keyboardSize=notification.userInfo?[UIResponder.keyboardFrameEndUserInfoKey] as?CGRect else {return}

        self.view.frame.origin.y = UISscreen.main.bounds.origin.y-keyboardSize.height
    }

    @objc func keyboardWillHide(notification:NSNotification){
        guard self.view.frame.origin.y!=0 else {return}

        self.view.frame.origin.y = 0
    }

    functextView(_textView:UITextView, shouldChangeTextInrange:NSRange, replacementTexttext:String) - >Bool{

        if(text=="\n"){
            hogeTextView.resignFirstResponder()
            return false
        }
        return true
    }
}