private @NonNls String errMsg(@NotNull RMNode<T> node) {
    System.gc();
    AtomicInteger alive = new AtomicInteger();
    node.processAliveKeys(t -> {
      alive.incrementAndGet();
      return true;
    });
    if (alive.get() > DUPLICATE_LIMIT) {
      return "Too many range markers (" + alive + ") registered for interval "+node;
    }

    return null;
  }
private @NonNls String errMsg(@NotNull RMNode<T> node)