Cómo obtener un lenguaje único a la traducción de varios idiomas

import 'package:i18n_extension/i18n_extension.dart';
extension Localization on String {
  //en,fr,es,de
  static var _t = Translations("en") +
      {
        "en": "Select Image",
		"te": "",
		"ta": "",
		"ml": "",
		"kn": "",
		"hi": ""
      } +
      {
        "en": "Remove",
		"te": "",
		"ta": "",
		"ml": "",
		"kn": "",
		"hi": ""
      };
  String get i18n => localize(this, _t);
}