How to use the esp-js.EspDecoratorUtil.getOrCreateMetaData function in esp-js

return function (target, name, descriptor) {
        Guard.stringIsNotEmpty(eventType, 'eventType passed to an eventTransformFor decorator must not be \'\'');
        let metadata: EspMetadata  = EspDecoratorUtil.getOrCreateMetaData(target.constructor);
        metadata.addEvent(
            name,
            eventType,
            DecoratorTypes.custom,
            observationStage,
            null
        );
        return descriptor;
    };
}

return function (target, name, descriptor) {
        Guard.stringIsNotEmpty(eventType, 'eventType passed to an observeStoreEvent decorator must not be \'\'');
        let metadata: EspMetadata  = EspDecoratorUtil.getOrCreateMetaData(target.constructor);
        metadata.addEvent(
            name,
            eventType,
            DecoratorTypes.custom,
            observationStage,
            null
        );
        return descriptor;
    };
}