public boolean isEmpty() {
      VirtualFile root = getVirtualFile();
      if (root == null) return true;
      RootType rootType = getRootType();
      Project project = Objects.requireNonNull(getProject());
      for (VirtualFile f : root.getChildren()) {
        if (!rootType.isIgnored(project, f)) return false;
      }
      return true;
    }
public boolean isEmpty()