code: func (a *CameraRollAction) MarshalJSON() ([]byte, error) {
  	return json.Marshal(&struct {
  		Type  ActionType `json:"type"`
  		Label string     `json:"label"`
  	}{
  		Type:  ActionTypeCameraRoll,
  		Label: a.Label,
  	})
  }
docs: // MarshalJSON method of CameraRollAction