BlackBerry 10: Load GroupDataModel data into a JSON file?

BlackBerry 10: Load GroupDataModel data into a JSON file?

I have a ListView in QML using a cpp GroupDataModel that is created from a
.json file in the assets folder. Items from this ListView are removed and
added to. In cpp how do I get the GroupDataModel data into the JSON file?
I know there is this:
JsonDataAccess jda;
jda.save(huh?, "/app/native/assets/employees.json");
How do I get the GroupDataModel data into a QVariant to put in the first
parameter of that function? I can't just stick my m_model GroupDataModel
in there; it causes an error.