private function processAggregateBodyHeaders(RequestCycle $cycle, AggregateBody $body)
{
$promise = $body->getHeaders();
$promise->when(function ($error, $result) use($cycle, $body) {
if ($error) {
$this->fail($cycle, $error);
} else {
$cycle->request->setAllHeaders($result);
$this->finalizeRequest($cycle);
}
});
}