docs: def invalidate(self, cls, id_field, id_val):
          """
          Invalidate the cache for a given Mongo object by deleting the cached
          data and the cache flag.
          """
          cache_key, flag_key = self.get_keys(cls, id_field, id_val)
  
          pipeline = self.redis.pipeline()
          pipeline.delete(cache_key)
          pipeline.delete(flag_key)
          pipeline.execute()