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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, key):
 """ Get a key from server, returning the value and its CAS key. This method is for API compatibility with other implementations. :param key: Key's name :type key: six.string_types :return: Returns (key data, value), or (None, None) if the value is not in cache. :rtype: object """

        for server in self.servers:
            value, cas = server.get(key)
            if value is not None:
                return value, cas
        return None, None