code: def _initialize(self):
          
          if not os.path.exists(self._logdir):
              raise CollectorError("Log directory %s not exists" % self._logdir)
  
          self.logger.info("Collector started, taking %s as parent directory"
                           "for all job logs." % self._logdir)
  
          # clear old records
          JobRecord.objects.filter().delete()
          TrialRecord.objects.filter().delete()
          ResultRecord.objects.filter().delete()
docs: Initialize collector worker thread, Log path will be checked first.
  
          Records in DB backend will be cleared.