code: def _get_hostname(self, hostname, sample, scraper_config):
          
          if (
              hostname is None
              and scraper_config['label_to_hostname'] is not None
              and scraper_config['label_to_hostname'] in sample[self.SAMPLE_LABELS]
          ):
              hostname = sample[self.SAMPLE_LABELS][scraper_config['label_to_hostname']]
              suffix = scraper_config['label_to_hostname_suffix']
              if suffix is not None:
                  hostname += suffix
  
          return hostname
docs: If hostname is None, look at label_to_hostname setting