@Nullable XmlFile findContext(final XmlFile file, Set<? super PsiElement> processed) {
        if (file != null) {
          processed.add(file);
          final XmlFile contextFile = getContextFile(file);
          return (contextFile == null || processed.contains(contextFile))? file : findContext(contextFile, processed);
        }
        return null;
      }
@Nullable XmlFile findContext(final XmlFile file, Set<? super PsiElement> processed)