private String getExportPackageListContent() {
        Set<String> pkgSet = listModels.stream().map(model -> model.appInfo.getPkgName()).collect(Collectors.toSet());
        return JsonFormatter.toPrettyJson(pkgSet);
    }
Null means we load all pkgs
android/app/src/main/java/now/fortuitous/thanos/power/SmartFreezeAppsViewModel.java