code: func reportQuota(c context.Context, payload proto.Message) error {
  	task, ok := payload.(*tasks.ReportQuota)
  	switch {
  	case !ok:
  		return errors.Reason("unexpected payload type %T", payload).Err()
  	case task.GetId() == "":
  		return errors.Reason("ID is required").Err()
  	}
  	p := &model.Project{
  		ID: task.Id,
  	}
  	if err := datastore.Get(c, p); err != nil {
  		return errors.Annotate(err, "failed to fetch project").Err()
  	}
  	mets := stringset.NewFromSlice(p.Config.Metric...)
  	regs := stringset.NewFromSlice(p.Config.Region...)
  	rsp, err := getCompute(c).Regions.List(p.Config.Project).Context(c).Do()
  	if err != nil {
  		if gerr, ok := err.(*googleapi.Error); ok {
  			logErrors(c, gerr)
  			return errors.Reason("failed to fetch quota").Err()
  		}
  		return errors.Annotate(err, "failed to fetch quota").Err()
  	}
  	for _, r := range rsp.Items {
  		if regs.Has(r.Name) {
  			for _, q := range r.Quotas {
  				if mets.Has(q.Metric) {
  					metrics.UpdateQuota(c, q.Limit, q.Usage, q.Metric, p.Config.Project, r.Name)
  				}
  			}
  		}
  	}
  	return nil
  }
docs: // reportQuota reports GCE quota utilization.