public function migrateOrders()
    {
        $start = $count = 0;
        $batch = Order::get()->sort('Created', 'ASC')->limit($start, self::$batch_size);
        while ($batch->exists()) {
            foreach ($batch as $order) {
                $this->migrate($order);
                echo '. ';
                $count++;
            }
            $start += self::$batch_size;
            $batch = $batch->limit($start, self::$batch_size);
        };
        echo "$count orders updated.\n<br/>";
    }