     private func notifyIsValidChanged() {
         self.delegate?.formInputValidated(in: self, isValid: isValid)
     }
-    
-    private func setupFormLayout(){
+
+    private func setupFormLayout() {
         NSLayoutConstraint.activate([
             // widthはscrollView.widthAnchor x ページ数
             formContentView.widthAnchor.constraint(equalTo: formScrollView.widthAnchor,
                                                    multiplier: CGFloat(4))
         ])
-        
+
         let pageWidth = formScrollView.frame.width
         let textFieldWidth = pageWidth
         let textFieldHeight = CGFloat(60.0)

                                                        y: 0.0,
                                                        width: textFieldWidth,
                                                        height: textFieldHeight))
        
        cardNumberTextField.borderStyle = .roundedRect
        expirationTextField.borderStyle = .roundedRect
        cvcTextField.borderStyle = .roundedRect
        cardHolderTextField.borderStyle = .roundedRect
        
        // placeholder
        cardNumberTextField.attributedPlaceholder = NSAttributedString(
            string: "payjp_card_form_number_placeholder".localized,

        expirationTextField.delegate = self
        cvcTextField.delegate = self
        cardHolderTextField.delegate = self

        formContentView.addArrangedSubview(cardNumberTextField)
        formContentView.addArrangedSubview(expirationTextField)
        formContentView.addArrangedSubview(cvcTextField)
        formContentView.addArrangedSubview(cardHolderTextField)

        formScrollView.contentSize = CGSize(width: pageWidth * CGFloat(4), height: textFieldHeight)
    }

