code: def DeleteOldCronJobRuns(self, cutoff_timestamp, cursor=None):
      
      query = "DELETE FROM cron_job_runs WHERE write_time < FROM_UNIXTIME(%s)"
      cursor.execute(query,
                     [mysql_utils.RDFDatetimeToTimestamp(cutoff_timestamp)])
docs: Deletes cron job runs that are older then the given timestamp.