private Map<VirtualFile, Collection<VirtualFile>> findFilesWithoutAttrs(Map<VirtualFile, Collection<VirtualFile>> filesByRoots) {
    Map<VirtualFile, Collection<VirtualFile>> filesWithoutAttrsByRoot = new HashMap<>();
    for (Map.Entry<VirtualFile, Collection<VirtualFile>> entry : filesByRoots.entrySet()) {
      VirtualFile root = entry.getKey();
      Collection<VirtualFile> files = entry.getValue();
      Collection<VirtualFile> filesWithoutAttrs = findFilesWithoutAttrs(root, files);
      if (!filesWithoutAttrs.isEmpty()) {
        filesWithoutAttrsByRoot.put(root, filesWithoutAttrs);
      }
    }
    return filesWithoutAttrsByRoot;
  }
private Map<VirtualFile, Collection<VirtualFile>> findFilesWithoutAttrs(Map<VirtualFile, Collection<VirtualFile>> filesByRoots)