Use of undeclared type 'UNUserNotificationCenter'

i want to show banner of push notification when app is in foreground. And i implementing this method to show notification:

func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void)
        {
            completionHandler([.alert, .badge, .sound])
        }

but this error received Use of undeclared type 'UNUserNotificationCenter'