navJson method
Implementation
Map<String, dynamic> navJson(SummaryArticle article) {
final next = summary.nextArticle(article);
final prev = summary.prevArticle(article);
return {
'title': article.title,
'level': article.level,
'depth': article.depth,
if (next != null) 'next': next.json,
if (prev != null) 'previous': prev.json,
};
}