title: How to detect APScheduler's running jobs?
body: <p>I have some recurring jobs run frequently or last for a while.
  It seems that Scheduler().get_jobs() will only return the list of scheduled jobs that are not currently running, so I cannot determine if a job with certain id do not exists or is actually running.</p>
  
  <p>How may I test if a job is running or not in this situation?</p>
  
  <p>(I set up those jobs not the usual way, (because I need them to run in a random interval, not fixed interval), they are jobs that execute only once, but will add a job with the same id by the end of their execution, and they will stop doing so when reaching a certain threshold.)</p>