code: def _run_data_engine(self, start_timeperiod, end_timeperiod):
          
          collection_name = context.process_context[self.process_name].source
          cursor = self.ds.cursor_batch(collection_name,
                                        start_timeperiod,
                                        end_timeperiod)
          for document in cursor:
              self._process_single_document(document)
              self.performance_tracker.increment_success()
  
          self._cursor_exploited()
          msg = 'Cursor exploited after fetching {0} documents'.format(self.performance_tracker.success_per_job)
          self.logger.info(msg)
docs: regular data engine