@Nullable
 private PsiFile getFile() {
   final XmlElement element = getContextElement();
   if (element == null) {
     return null;
   }
   return element.getContainingFile().getOriginalFile();
 }
 protected XsltContextProviderBase(XmlElement element) {
   final Project project = element.getProject();
   myFileAssociationsManager = FileAssociationsManager.getInstance(project);
   myContextElement =
       SmartPointerManager.getInstance(project).createSmartPsiElementPointer(element);
   attachTo(element);
 }