<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add(self, key, value, expire=0, noreply=None):
 """ 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). """

        if noreply is None:
            noreply = self.default_noreply
        return self._store_cmd(b'add', {key: value}, expire, noreply)[key]