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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 _parse_pool_transaction_file( ledger, nodeReg, cliNodeReg, nodeKeys, activeValidators, ledger_size=None):
 """ helper function for parseLedgerForHaAndKeys """

        for _, txn in ledger.getAllTxn(to=ledger_size):
            if get_type(txn) == NODE:
                txn_data = get_payload_data(txn)
                nodeName = txn_data[DATA][ALIAS]
                clientStackName = nodeName + CLIENT_STACK_SUFFIX
                nHa = (txn_data[DATA][NODE_IP], txn_data[DATA][NODE_PORT]) \
                    if (NODE_IP in txn_data[DATA] and NODE_PORT in txn_data[DATA]) \
                    else None
                cHa = (txn_data[DATA][CLIENT_IP], txn_data[DATA][CLIENT_PORT]) \
                    if (CLIENT_IP in txn_data[DATA] and CLIENT_PORT in txn_data[DATA]) \
                    else None
                if nHa:
                    nodeReg[nodeName] = HA(*nHa)
                if cHa:
                    cliNodeReg[clientStackName] = HA(*cHa)

                try:
                    # TODO: Need to handle abbreviated verkey
                    key_type = 'verkey'
                    verkey = cryptonymToHex(str(txn_data[TARGET_NYM]))
                    key_type = 'identifier'
                    cryptonymToHex(get_from(txn))
                except ValueError:
                    logger.exception(
                        'Invalid {}. Rebuild pool transactions.'.format(key_type))
                    exit('Invalid {}. Rebuild pool transactions.'.format(key_type))

                nodeKeys[nodeName] = verkey

                services = txn_data[DATA].get(SERVICES)
                if isinstance(services, list):
                    if VALIDATOR in services:
                        activeValidators.add(nodeName)
                    else:
                        activeValidators.discard(nodeName)