code: func (a *URIAction) MarshalJSON() ([]byte, error) {
  	return json.Marshal(&struct {
  		Type   ActionType       `json:"type"`
  		Label  string           `json:"label,omitempty"`
  		URI    string           `json:"uri"`
  		AltURI *URIActionAltURI `json:"altUri,omitempty"`
  	}{
  		Type:   ActionTypeURI,
  		Label:  a.Label,
  		URI:    a.URI,
  		AltURI: a.AltURI,
  	})
  }
docs: // MarshalJSON method of URIAction