public static String getCategory(Notification notification) {
        if (Build.VERSION.SDK_INT >= 21) {
            return notification.category;
        } else {
            return null;
        }
    }
Get the category of this notification in a backwards compatible
manner.

@param notification The notification to inspect.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/compat/NotificationCompat.java