def METHOD_NAME(op, key, nonce, signer_key, last_block_hash, node):
    if op == 'read':
        args = key
        fn = 'read_value'
    else:
        args = key + random_u64()
        fn = 'write_key_value'
    tx = transaction.sign_function_call_tx(signer_key, signer_key.account_id,
                                           fn, args, 300 * account.TGAS, 0,
                                           nonce, last_block_hash)
    return node.send_tx(tx).get('result')