code: def __x_google_quota_descriptor(self, metric_costs):
      
      return {
          'metricCosts': {
              metric: cost for (metric, cost) in metric_costs.items()
          }
      } if metric_costs else None
docs: Describes the metric costs for a call.
  
      Args:
        metric_costs: Dict of metric definitions to the integer cost value against
          that metric.
  
      Returns:
        A dict descriptor describing the Quota limits for the endpoint.