getTexts() {
				return Promise.reject("translation.getTexts is not implemented");
			}
Interface called to get the translatable texts for the given source & target language for the given application

@param {object} mPropertyBag - Property bag
@param {sap.ui.fl.Layer} mPropertyBag.layer - Layer
@param {string} mPropertyBag.sourceLanguage - Source language for for which the request should be made
@param {string} mPropertyBag.targetLanguage - Target language for for which the request should be made
@param {string} mPropertyBag.reference - Flex reference
@returns {Promise} Promise resolving after the download was started;
rejects if an error occurs