private static @Nullable XsdNamespaceBuilder getFileNamespace(@NotNull VirtualFile file, @NotNull Project project) {
    if (FileTypeRegistry.getInstance().isFileOfType(file, DTDFileType.INSTANCE)) {
      return new XsdNamespaceBuilder(file.getName(), "", Collections.emptyList(), Collections.emptyList());
    }
    Map<String, XsdNamespaceBuilder> data = FileBasedIndex.getInstance().getFileData(NAME, file, project);
    return ContainerUtil.getFirstItem(data.values());
  }
private static @Nullable XsdNamespaceBuilder getFileNamespace(@NotNull VirtualFile file, @NotNull Project project)