code: def retain_identities(self, retention_time):
          
          enrich_es = self.conf['es_enrichment']['url']
          sortinghat_db = self.db
          current_data_source = self.get_backend(self.backend_section)
          active_data_sources = self.config.get_active_data_sources()
  
          if retention_time is None:
              logger.debug("[identities retention] Retention policy disabled, no identities will be deleted.")
              return
  
          if retention_time <= 0:
              logger.debug("[identities retention] Retention time must be greater than 0.")
              return
  
          retain_identities(retention_time, enrich_es, sortinghat_db, current_data_source, active_data_sources)
docs: Retain the identities in SortingHat based on the `retention_time`
          value declared in the setup.cfg.
  
          :param retention_time: maximum number of minutes wrt the current date to retain the SortingHat data