private function tradesData(array $trades)
    {
        $output = [];
        foreach ($trades as $trade) {
            $price = $trade['p'];
            $quantity = $trade['q'];
            $timestamp = $trade['T'];
            $maker = $trade['m'] ? 'true' : 'false';
            $output[] = [
                "price" => $price,
                "quantity" => $quantity,
                "timestamp" => $timestamp,
                "maker" => $maker,
            ];
        }
        return $output;
    }