public function jsonSerialize() {

		$request = new \WP_REST_Request( 'GET', '/pressbooks/v2/metadata' );
		$meta = new \Pressbooks\Api\Endpoints\Controller\Metadata();
		$metadata = $meta
			->get_item( $request )
			->get_data();

		return apply_filters( 'pb_json_metadata', $metadata );
	}