persist method
Implementation
Future<void> persist(String key, dynamic value) async {
assert(_box != null, 'the store is not connected');
final update = _box!.containsKey(key);
await _box!.put(key, value);
_notifyChangesListeners(
update ? TStoreChangeType.update : TStoreChangeType.add,
key: key,
value: value,
);
}