code: def get_intern_pattern (self, url=None):
          
          if url is None:
              url = absolute_url(self.base_url, self.base_ref, self.parent_url)
          if not url:
              return None
          return get_intern_pattern(url)
docs: Get pattern for intern URL matching.
  
          @return non-empty regex pattern or None
          @rtype String or None