public static void addNotification(@Nullable DiffNotificationProvider provider, @NotNull UserDataHolder holder) {
    if (provider == null) return;
    List<DiffNotificationProvider> newProviders = new ArrayList<>(getNotificationProviders(holder));
    newProviders.add(provider);
    holder.putUserData(DiffUserDataKeys.NOTIFICATION_PROVIDERS, newProviders);
  }
public static void addNotification(@Nullable DiffNotificationProvider provider, @NotNull UserDataHolder holder)