anchor.diff:    ///
     Future updateSyncInfo(T record, String syncId, String syncVersion) async {
       var txn = storeTransaction(true);
  -    DbSyncedRecord existingRecord = await txnGet(txn, record.id);
  +    DbSyncedRecordBase existingRecord = await txnGet(txn, record.id);
       if (existingRecord != null) {
         // Check version before changing the dirty flag
         if (record.version == existingRecord.version) {
  
positive.code:   Future<T> getFirstDirty() async {
      var txn = indexTransaction(dirtyIndex);
      var id = await txn.getKey(1); // 1 is dirty
      DbSyncedRecord record;
      if (id != null) {
        record = await txnGet(txn.store, id);
      }
  
negative.code:     if (existingRecord != null) {
        record.version = existingRecord.version + 1;
      } else {
        record.version = 1;
      }
      /*
        if (list.version != existingList.version) {
  