code: def process(self, items_block):
          
  
          out_items = []
  
          for hit in items_block:
              if __name__ == '__main__':
                  hit['_source']['metadata__enriched_on'] = datetime.datetime_utcnow().isoformat()
              out_items.append(hit)
  
          return self.ProcessResults(processed=0, out_items=out_items)
docs: Return items as they come, updating their metadata__enriched_on field.
  
          :param items_block:
          :return: hits blocks as they come, updating their metadata__enriched_on field. Namedtuple containing:
              - processed: number of processed hits
              - out_items: a list containing items ready to be written.