code: def add(self, key, value, expire=0, noreply=None):
          
          if noreply is None:
              noreply = self.default_noreply
          return self._store_cmd(b'add', {key: value}, expire, noreply)[key]
docs: The memcached "add" command.
  
          Args:
            key: str, see class docs for details.
            value: str, see class docs for details.
            expire: optional int, number of seconds until the item is expired
                    from the cache, or zero for no expiry (the default).
            noreply: optional bool, True to not wait for the reply (defaults to
                     self.default_noreply).
  
          Returns:
            If noreply is True, the return value is always True. Otherwise the
            return value is True if the value was stored, and False if it was
            not (because the key already existed).