code: func GetPendingCounts(c context.Context, builders []string) ([]int, error) {
  	entities := make([]builderEntity, len(builders))
  	for i, b := range builders {
  		parts := strings.SplitN(b, "/", 2)
  		if len(parts) < 2 {
  			return nil, errors.Reason("builder does not have a slash: %q", b).Err()
  		}
  		entities[i].MasterKey = datastore.MakeKey(c, masterKind, parts[0])
  		entities[i].Name = parts[1]
  	}
  	if err := datastore.Get(c, entities); err != nil {
  		for _, e := range err.(errors.MultiError) {
  			if e != nil && e != datastore.ErrNoSuchEntity {
  				return nil, err
  			}
  		}
  	}
  
  	counts := make([]int, len(entities))
  	for i, e := range entities {
  		counts[i] = e.PendingCount
  	}
  	return counts, nil
  }
docs: // GetPendingCounts returns numbers of pending builds in builders.
  // builders must be a list of slash-separated master, builder names.