Jose\Behaviour\EncrypterTrait::getKeyManagementMode PHP Method

    private function getKeyManagementMode(Object\JWEInterface $jwe)
    {
        $mode = null;
        $recipients = $jwe->getRecipients();
        foreach ($recipients as $recipient) {
            $complete_headers = array_merge($jwe->getSharedProtectedHeaders(), $jwe->getSharedHeaders(), $recipient->getHeaders());
            Assertion::keyExists($complete_headers, 'alg', 'Parameter "alg" is missing.');
            $key_encryption_algorithm = $this->getJWAManager()->getAlgorithm($complete_headers['alg']);
            Assertion::isInstanceOf($key_encryption_algorithm, Algorithm\KeyEncryptionAlgorithmInterface::class, sprintf('The key encryption algorithm "%s" is not supported or not a key encryption algorithm instance.', $complete_headers['alg']));
            if (null === $mode) {
                $mode = $key_encryption_algorithm->getKeyManagementMode();
            } else {
                Assertion::true($this->areKeyManagementModesCompatible($mode, $key_encryption_algorithm->getKeyManagementMode()), 'Foreign key management mode forbidden.');
            }
        }
        return $mode;
    }