code: def exists(self):
          
          try:
              self.es.get(index=self.marker_index, doc_type=self.marker_doc_type, id=self.marker_index_document_id())
              return True
          except elasticsearch.NotFoundError:
              logger.debug('Marker document not found.')
          except elasticsearch.ElasticsearchException as err:
              logger.warn(err)
          return False
docs: Test, if this task has been run.