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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 cache_id(self) -> str: """ Return identifier for archivable caches, computing it first and retaining it if need be. Raise AbsentPool if ledger configuration is not yet available. :param name: pool name :return: archivable cache identifier """


        if self._cache_id:
            return self._cache_id

        with open(join(expanduser('~'), '.indy_client', 'pool', self.name, '{}.txn'.format(self.name))) as fh_genesis:
            genesis = [json.loads(line) for line in fh_genesis.readlines() if line]

        hps = []
        for gen_txn in genesis:
            hps.append(self.protocol.genesis_host_port(gen_txn))
        hps.sort()  # canonicalize to make order irrelevant
        self._cache_id = ':'.join('{}:{}'.format(hp[0], hp[1]) for hp in hps)

        return self._cache_id