private boolean isXmlFile(XmlElement element) {
        if (isXml == null) {
          final PsiFile file = element.getContainingFile();
          isXml = file instanceof XmlFile && !InjectedLanguageManager.getInstance(element.getProject()).isInjectedFragment(file);
        }
        return isXml.booleanValue();
      }
private boolean isXmlFile(XmlElement element)