code: def LeaseCronJobs(self, cronjob_ids=None, lease_time=None):
      
      leased_jobs = []
  
      now = rdfvalue.RDFDatetime.Now()
      expiration_time = now + lease_time
  
      for job in itervalues(self.cronjobs):
        if cronjob_ids and job.cron_job_id not in cronjob_ids:
          continue
        existing_lease = self.cronjob_leases.get(job.cron_job_id)
        if existing_lease is None or existing_lease[0] < now:
          self.cronjob_leases[job.cron_job_id] = (expiration_time,
                                                  utils.ProcessIdString())
          job = job.Copy()
          job.leased_until, job.leased_by = self.cronjob_leases[job.cron_job_id]
          leased_jobs.append(job)
  
      return leased_jobs
docs: Leases all available cron jobs.