code: def setnx(self, name, value):
          
          with self.pipe as pipe:
              return pipe.setnx(self.redis_key(name),
                                self.valueparse.encode(value))
docs: Set the value as a string in the key only if the key doesn't exist.
  
          :param name: str     the name of the redis key
          :param value:
          :return: Future()