code: def sadd(self, key, *values):
          
          if len(values) == 0:
              raise ResponseError("wrong number of arguments for 'sadd' command")
          redis_set = self._get_set(key, 'SADD', create=True)
          before_count = len(redis_set)
          redis_set.update(map(self._encode, values))
          after_count = len(redis_set)
          return after_count - before_count
docs: Emulate sadd.