use mdbook_preprocessor::book::{BookItem, Chapter};
pub fn decorate_chapters<F>(item: &mut BookItem, decorate: &F)
where
F: Fn(&mut Chapter),
{
if let BookItem::Chapter(ch) = item {
decorate(ch);
for sub in &mut ch.sub_items {
decorate_chapters(sub, decorate);
}
}
}