@acquire<EOL><INDENT>def gets(self, conn, key, default=None):<DEDENT>
values, cas_tokens = yield from self._multi_get(<EOL>conn, key, with_cas=True)<EOL>return values.get(key, default), cas_tokens.get(key)<EOL>
Gets a single value from the server together with the cas token.

        :param key: ``bytes``, is the key for the item being fetched
        :param default: default value if there is no value.
        :return: ``bytes``, ``bytes tuple with the value and the cas