code: def ReturnLeasedCronJobs(self, jobs, cursor=None):
      
      if not jobs:
        return
  
      unleased_jobs = []
  
      conditions = []
      args = []
      for job in jobs:
        if not job.leased_by or not job.leased_until:
          unleased_jobs.append(job)
          continue
  
        conditions.append("""
        (job_id = %s AND leased_until = FROM_UNIXTIME(%s) AND leased_by = %s)
        """)
        args += [
            job.cron_job_id,
            mysql_utils.RDFDatetimeToTimestamp(job.leased_until), job.leased_by
        ]
  
      if conditions:
        query = ("UPDATE cron_jobs "
                 "SET leased_until=NULL, leased_by=NULL "
                 "WHERE ") + " OR ".join(conditions)
        returned = cursor.execute(query, args)
  
      if unleased_jobs:
        raise ValueError("CronJobs to return are not leased: %s" % unleased_jobs)
      if returned != len(jobs):
        raise ValueError("%d cronjobs in %s could not be returned." %
                         ((len(jobs) - returned), jobs))
docs: Makes leased cron jobs available for leasing again.