code: func (ra *RegistrationAuthorityImpl) enforceNameCounts(
  	ctx context.Context,
  	names []string,
  	limit ratelimit.RateLimitPolicy,
  	regID int64,
  	countFunc certCountRPC) ([]string, error) {
  
  	now := ra.clk.Now()
  	windowBegin := limit.WindowBegin(now)
  	counts, err := countFunc(ctx, names, windowBegin, now)
  	if err != nil {
  		return nil, err
  	}
  
  	var badNames []string
  	for _, entry := range counts {
  		// Should not happen, but be defensive.
  		if entry.Count == nil || entry.Name == nil {
  			return nil, fmt.Errorf("CountByNames_MapElement had nil Count or Name")
  		}
  		if int(*entry.Count) >= limit.GetThreshold(*entry.Name, regID) {
  			badNames = append(badNames, *entry.Name)
  		}
  	}
  	return badNames, nil
  }
docs: // enforceNameCounts uses the provided count RPC to find a count of certificates
  // for each of the names. If the count for any of the names exceeds the limit
  // for the given registration then the names out of policy are returned to be
  // used for a rate limit error.