protected @NotNull Collection<PsiFileSystemItem> toFileSystemItems(@NotNull Collection<? extends VirtualFile> files) {
    final PsiManager manager = getElement().getManager();
    return ContainerUtil.mapNotNull(files, file -> file != null && file.isValid() ? manager.findDirectory(file) : null);
  }
protected @NotNull Collection<PsiFileSystemItem> toFileSystemItems(@NotNull Collection<? extends VirtualFile> files)