Swift AppDeligate does not conform to protocol 'MessagingDelegate'

Using Swift2.3 and Xcode 8
I upgraded Firebase to version 4

I followed all mentioned Changes in the new version https://firebase.google.com/docs/reference/ios/naming-migration-guide#changes_in_the_new_version

Stil I get one error saying

Type 'AppDelegate' does not conform to protocol 'MessagingDelegate'

I dono what this method is changed to or which new method I need to add. kindly help me

class Appdelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate, MessagingDelegate
{
    func application(remoteMessage: MessagingRemoteMessage)
    {
        let remoteMsgVar = remoteMessage.appData
        print("remoteMessage : ", remoteMsgVar)
    }
}