Using Tableview to display items in descending order with childByAutoId

I am trying to display a data set in descending order by snap.key in a firebaseUi TableView

Firebase *firebaseRef = [[Firebase alloc] initWithUrl:@"firebaseio.com/data"];

    self.dataSource = [[FirebaseTableViewDataSource alloc] initWithRef:firebaseRef cellReuseIdentifier:@"cell" view:self.tableView];

    [self.dataSource populateCellWithBlock:^(UITableViewCell *cell, FDataSnapshot *snap){
        // Populate cell as you see fit, like as below

        cell.textLabel.text = snap.value[@"Data"];


    }];