code: func OptFieldTypeSet(cacheType string, cacheSize uint32) FieldOption {
  	return func(fo *FieldOptions) error {
  		if fo.Type != "" {
  			return errors.Errorf("field type is already set to: %s", fo.Type)
  		}
  		fo.Type = FieldTypeSet
  		fo.CacheType = cacheType
  		fo.CacheSize = cacheSize
  		return nil
  	}
  }
docs: // OptFieldTypeSet is a functional option on FieldOptions
  // used to specify the field as being type `set` and to
  // provide any respective configuration values.