code: def _create_core_dns_instance(self, instance):
          
          endpoint = instance.get('prometheus_url')
          if endpoint is None:
              raise ConfigurationError("Unable to find prometheus endpoint in config file.")
  
          metrics = [DEFAULT_METRICS, GO_METRICS]
          metrics.extend(instance.get('metrics', []))
  
          instance.update({'prometheus_url': endpoint, 'namespace': 'coredns', 'metrics': metrics})
  
          return instance
docs: Set up coredns instance so it can be used in OpenMetricsBaseCheck