Gaufrette\Adapter\AwsS3::setMetadata PHP Method

    public function setMetadata($key, $metadata)
    {
        // BC with AmazonS3 adapter
        if (isset($metadata['contentType'])) {
            $metadata['ContentType'] = $metadata['contentType'];
            unset($metadata['contentType']);
        }
        $this->metadata[$key] = $metadata;
    }