mysqld_exporter version: output of mysqld_exporter --version

mysqld_exporter, version 0.12.1

MySQL server version

mysqld Ver 5.6.40-84.0-56 for Linux on x86_64 (Percona XtraDB Cluster (GPL)

What did you expect to see?

went to find some metrics about mysql transaction duration time,but did‘t find it

In daily work,I usually use to following sql to check long transaction whether exist and other info anout long transaction :
SELECT trx_id, trx_started, NOW() - trx_started AS trx_duration_seconds
, CONCAT('KILL ', id, ' ;') AS kill_session_id
, user
, IF(LEFT(HOST, LOCATE(':', host) - 1) = '', host, LEFT(HOST, LOCATE(':', host) - 1)) AS host
, command, time
, REPLACE(SUBSTRING(info, 1, 25), '
', '') AS info_25
FROM information_schema.innodb_trx
JOIN information_schema.processlist ON innodb_trx.trx_mysql_thread_id = processlist.id
WHERE NOW() - trx_started > 10
ORDER BY trx_started DESC;

Where i can find metrics about mysql transaction duration?

Looking forward to a reply.