code: def ScheduleSystemCronJobs(names=None):
    
  
    errors = []
    disabled_classes = config.CONFIG["Cron.disabled_cron_jobs"]
    for name in disabled_classes:
      try:
        cls = registry.SystemCronJobRegistry.CronJobClassByName(name)
      except ValueError:
        errors.append("Cron job not found: %s." % name)
        continue
  
    if names is None:
      names = iterkeys(registry.SystemCronJobRegistry.SYSTEM_CRON_REGISTRY)
  
    for name in names:
  
      cls = registry.SystemCronJobRegistry.CronJobClassByName(name)
  
      enabled = cls.enabled and name not in disabled_classes
      system = rdf_cronjobs.CronJobAction.ActionType.SYSTEM_CRON_ACTION
      args = rdf_cronjobs.CronJobAction(
          action_type=system,
          system_cron_action=rdf_cronjobs.SystemCronAction(job_class_name=name))
  
      job = rdf_cronjobs.CronJob(
          cron_job_id=name,
          args=args,
          enabled=enabled,
          frequency=cls.frequency,
          lifetime=cls.lifetime,
          allow_overruns=cls.allow_overruns)
      data_store.REL_DB.WriteCronJob(job)
  
    if errors:
      raise ValueError(
          "Error(s) while parsing Cron.disabled_cron_jobs: %s" % errors)
docs: Schedules all system cron jobs.