code: func groupByLabel(entries interface{}, label string) (map[string][]interface{}, error) {
  	getLabel := func(v interface{}) (interface{}, error) {
  		if container, ok := v.(RuntimeContainer); ok {
  			if value, ok := container.Labels[label]; ok {
  				return value, nil
  			}
  			return nil, nil
  		}
  		return nil, fmt.Errorf("Must pass an array or slice of RuntimeContainer to 'groupByLabel'; received %v", v)
  	}
  	return generalizedGroupBy("groupByLabel", entries, getLabel, func(groups map[string][]interface{}, value interface{}, v interface{}) {
  		groups[value.(string)] = append(groups[value.(string)], v)
  	})
  }
docs: // groupByLabel is the same as groupBy but over a given label