private static @Nullable PackageNode getSelectedPackage(final Tree tree) {
    TreePath[] paths = tree.getSelectionPaths();
    if (paths == null || paths.length != 1) return null;
    PackageDependenciesNode node = (PackageDependenciesNode)paths[0].getLastPathComponent();
    if (node.isRoot()) return null;
    if (node instanceof PackageNode) {
      return (PackageNode)node;
    }
    if (node instanceof FileNode) {
      return (PackageNode)node.getParent();
    }
    if (node instanceof ModuleNode){
      return (PackageNode)node.getChildAt(0);
    }
    return null;
  }
private static @Nullable PackageNode getSelectedPackage(final Tree tree)