code: func ValidateUsages(usages []string) error {
  	validUsages := sets.NewString(api.KnownTokenUsages...)
  	invalidUsages := sets.NewString()
  	for _, usage := range usages {
  		if !validUsages.Has(usage) {
  			invalidUsages.Insert(usage)
  		}
  	}
  	if len(invalidUsages) > 0 {
  		return fmt.Errorf("invalid bootstrap token usage string: %s, valid usage options: %s", strings.Join(invalidUsages.List(), ","), strings.Join(api.KnownTokenUsages, ","))
  	}
  	return nil
  }
docs: // ValidateUsages validates that the passed in string are valid usage strings for bootstrap tokens.