code: def set_cache_url (self):
          
          # remove anchor from cached target url since we assume
          # URLs with different anchors to have the same content
          self.cache_url = urlutil.urlunsplit(self.urlparts[:4]+[u''])
          if self.cache_url is not None:
              assert isinstance(self.cache_url, unicode), repr(self.cache_url)
docs: Set the URL to be used for caching.