Notification in RxAction Example

Im RxSwift newbie. I think purpose of RxAction is demonstrate how to use Action, but is it cost much or complex to replace notification handling here ?
Are there anyway to implement this logic using RxSwift syntax ?
NotificationCenter.default.addObserver( self, selector: #selector(keyboardWillShow(_:)), name: NSNotification.Name.UIKeyboardWillShow, object: nil)