code: def get_default_metrics(config):
      
      archivers = list_archivers(config)
      default_metrics = []
  
      for archiver in archivers:
          index = get_archiver_index(config, archiver)
  
          if len(index) == 0:
              logger.warning("No records found in the index, no metrics available")
              return []
  
          operators = index[0]["operators"]
          for operator in operators:
              o = resolve_operator(operator)
              if o.cls.default_metric_index is not None:
                  metric = o.cls.metrics[o.cls.default_metric_index]
                  default_metrics.append("{0}.{1}".format(o.cls.name, metric.name))
      return default_metrics
docs: Get the default metrics for a configuration.
  
      :param config: The configuration
      :type  config: :class:`wily.config.WilyConfig`
  
      :return: Return the list of default metrics in this index
      :rtype: ``list`` of ``str``