     func expandableTextViewDidHidePlaceholder(_ textView: ExpandableTextView)
 }
 
+extension Notification.Name {
+    public static let didBecomeFirstResponder = Notification.Name("DidBecomeFirstResponder")
+    public static let didResignFirstResponder = Notification.Name("DidResignFirstResponder")
+}
+
 open class ExpandableTextView: UITextView {
 
     private let placeholder: UITextView = UITextView()

        self.commonInit()
    }

    override public init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        self.commonInit()

    }

    private func commonInit() {
        self.setupTextDidChangeObserver()
        self.configurePlaceholder()
        self.updatePlaceholderVisibility()
    }
