code: def unregister(self, slug):
          
  
          if slug not in self._registry:
              raise NotRegistered('The slug %s is not registered' % slug)
          bundle = self._registry[slug]
          if bundle._meta.model and bundle._meta.primary_model_bundle:
              self.unregister_model(bundle._meta.model)
  
          del self._registry[slug]
          del self._order[slug]
docs: Unregisters the given url.
  
          If a slug isn't already registered, this will raise NotRegistered.