Error in IdleTimerManager.java

[ErYogeshPatil]

public static void deactivate(@NotNull final Activity activity, final String tag) {
^
symbol: class NotNull
location: class IdleTimerManager

error in this code in IdleTimerManager.java

public static void activate(@NotNull final Activity activity, final String tag) {
if (tags.isEmpty()) {
activity.runOnUiThread(() -> {
activity.getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
});
}
tags.add((tag == null ? "" : tag));
}

public static void deactivate(@NotNull final Activity activity, final String tag) {
    if (tags.size() == 1 && tags.contains((tag))) {
        activity.runOnUiThread(() -> {
            activity.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        });
    }
    tags.remove((tag == null ? "" : tag));
}