protected function determineResponseType($availableTypes)
    {
        $bestType = $this->contentNegotiation->negotiateMedia($availableTypes);
        if ($bestType instanceof Accept\Media\MediaValue) {
            $contentType = $bestType->getValue();
            $subType = $bestType->getSubtype();
            $this->contentType = $contentType;
            return $contentType;
        }
    }