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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def gets(self, conn, key, default=None):
 """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 """

        values, cas_tokens = yield from self._multi_get(
            conn, key, with_cas=True)
        return values.get(key, default), cas_tokens.get(key)