private static void groupByNullness(SliceRootNode oldRoot, SliceRootNode root) {
    SliceUsage rootUsage = oldRoot.getCachedChildren().get(0).getValue();
    SliceManager.getInstance(Objects.requireNonNull(root.getProject()))
      .createToolWindow(true, root, true,
                        SliceManager.getElementDescription(null, Objects.requireNonNull(rootUsage).getElement(),
                                                           JavaBundle.message("tab.title.slices.grouped.by.nullness")));
  }
private static void groupByNullness(SliceRootNode oldRoot, SliceRootNode root)