private static String setPackageSuspended(final Context context, final Stream<String> pkgs, final boolean suspended) {
		final String[] failed = new DevicePolicies(context).invoke(DevicePolicyManager::setPackagesSuspended, pkgs.toArray(String[]::new), suspended);
		return failed.length == 0 ? null : "Failed packages: " + Arrays.toString(failed);
	}
@return null for success, or error message for debugging purpose (NOT part of the API protocol).
engine/src/main/java/com/oasisfeng/island/api/ApiDispatcher.java