code: def register_cache(self, cache_group):
          
  
          if cache_group.key in self._registry:
              raise Exception("%s is already registered" % cache_group.key)
          self._registry[cache_group.key] = cache_group
docs: Register a cache_group with this manager.
  
          Use this method to register more complicated
          groups that you create yourself. Such as if you
          need to register several models each with different
          parameters.
  
          :param cache_group: The group to register. \
          The group is registered with the cache_group key attribute. \
          Raises an exception if the key is already registered.