How to get the currently-running jobs via Prometheus

Hello there,

I would like to monitor my runners. Aside from many other measures, I would like to have a number of currently-running jobs.

The doc say:

can view things like the number of currently-running jobs

GitLab Runner | GitLab

However, I cannot see any metrics that seems to hold this information. Maybe a computation on the gitlab_runner_api_request_statuses_total but nor sure how to do it.