code: def ensure_cache_id(self, cache_id_obj):
          
          cache_id = self._get_canonical_id(cache_id_obj)
          if cache_id != self._cache_id_obj:
              raise ValueError(
                  "cache mismatch {0} != {1}".format(
                      cache_id, self._cache_id_obj))
docs: Ensure the integrity of the cache id object.