code: def get_next_batch(self):
          
          if self.iterator is None:
              self.iterator = self.iteritems()
  
          count = 0
          while count < self.batch_size:
              count += 1
              yield next(self.iterator)
          self.logger.debug('Done reading batch')
docs: This method is called from the manager. It must return a list or a generator
          of BaseRecord objects.
          When it has nothing else to read, it must set class variable "finished" to True.