@Override
  public @NotNull XmlFileHeader getXmlFileHeader(@NotNull XmlFile file) {
    if (FileBasedIndex.getInstance().getFileBeingCurrentlyIndexed() != null) {
      return calcXmlFileHeader(file);
    }

    return CachedValuesManager.getCachedValue(file, () -> new CachedValueProvider.Result<>(calcXmlFileHeader(file), file));
  }
@Override
  public @NotNull XmlFileHeader getXmlFileHeader(@NotNull XmlFile file)