code: func ValidateInclusion(ch *Changeset, field string, values []interface{}, opts ...Option) {
  	val, exist := ch.changes[field]
  	if !exist {
  		return
  	}
  
  	options := Options{
  		message: ValidateInclusionErrorMessage,
  	}
  	options.apply(opts)
  
  	invalid := true
  	for _, inval := range values {
  		if val == inval {
  			invalid = false
  			break
  		}
  	}
  
  	if invalid {
  		r := strings.NewReplacer("{field}", field, "{values}", fmt.Sprintf("%v", values))
  		AddError(ch, field, r.Replace(options.message))
  	}
  }
docs: // ValidateInclusion validates a change is included in the given values.