code: def add(self, key, value, time=0, compress_level=-1):
          
          server = self._get_server(key)
          return server.add(key, value, time, compress_level)
docs: Add a key/value to server ony if it does not exist.
  
          :param key: Key's name
          :type key: six.string_types
          :param value: A value to be stored on server.
          :type value: object
          :param time: Time in seconds that your key will expire.
          :type time: int
          :param compress_level: How much to compress.
              0 = no compression, 1 = fastest, 9 = slowest but best,
              -1 = default compression level.
          :type compress_level: int
          :return: True if key is added False if key already exists
          :rtype: bool