@acquire<EOL><INDENT>def replace(self, conn, key, value, exptime=<NUM_LIT:0>):<DEDENT>
flags = <NUM_LIT:0>  <EOL>return (yield from self._storage_command(<EOL>conn, b'<STR_LIT:replace>', key, value, flags, exptime))<EOL>
Store this data, but only if the server *does*
        already hold data for this key.

        :param key: ``bytes``, is the key of the item.
        :param value: ``bytes``,  data to store.
        :param exptime: ``int`` is expiration time. If it's 0, the
        item never expires.
        :return: ``bool``, True in case of success.