@Nullable
  protected List<XmlFile> findExternalAnnotationsXmlFiles(@NotNull PsiModifierListOwner listOwner) {
    List<PsiFile> psiFiles = findExternalAnnotationsFiles(listOwner);
    if (psiFiles == null) {
      return null;
    }
    List<XmlFile> xmlFiles = new ArrayList<>();
    for (PsiFile psiFile : psiFiles) {
      if (psiFile instanceof XmlFile) {
        xmlFiles.add((XmlFile)psiFile);
      }
    }
    return xmlFiles;
  }
@Nullable
  protected List<XmlFile> findExternalAnnotationsXmlFiles(@NotNull PsiModifierListOwner listOwner)