Bref's Uploaded Files Not Deleted in Event-Driven Functions

private static function parseBodyAndUploadedFiles(HttpRequestEvent $event): array
{
    $bodyString = $event->getBody();
    $files = [];
    $parsedBody = null;
    $contentType = $event->getContentType();
    if ($contentType !== null && $event->getMethod() === 'POST') {
        if (str_starts_with($contentType, 'application/x-www-form-urlencoded')) {
            parse_str($bodyString, $parsedBody);
        } else {
            $document = new Part("Content-type: $contentType\r\n\r\n" . $bodyString);
            if ($document->isMultiPart()) {
                $parsedBody = [];
                foreach ($document->getParts() as $part) {
                    if ($part->isFile()) {
                        $tmpPath = tempnam(sys_get_temp_dir(), 'bref_upload_');
                        if ($tmpPath === false) {
                            throw new RuntimeException('Unable to create a temporary directory');
                        }
                        file_put_contents($tmpPath, $part->getBody());
                        $file = new UploadedFile($tmpPath, filesize($tmpPath), UPLOAD_ERR_OK, $part->getFileName(), $part->getMimeType());

                        self::parseKeyAndInsertValueInArray($files, $part->getName(), $file);
                    } else {
                        self::parseKeyAndInsertValueInArray($parsedBody, $part->getName(), $part->getBody());
                    }
                }
            }
        }
    }
    return [$files, $parsedBody];
}

<?php

namespace App;

require __DIR__ . '/vendor/autoload.php';

use Nyholm\Psr7\Response;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\RequestHandlerInterface;

class MyHttpHandler implements RequestHandlerInterface
{
    public function handle(ServerRequestInterface $request): ResponseInterface
    {
        return new Response(200, [], exec("ls -lah /tmp/bref_upload* | wc -l"));
    }
}

return new MyHttpHandler();