$def with (doc, decorations=None, cta=True, availability=None, extra=None) $ availability = availability or doc.get('availability') or {} $ ocaid = availability.get('identifier') $ is_work = doc.get('type', {}).get('key') == '/type/work' $ book_url = doc.url() if is_work else doc.key $ cover_ids = [cover for cover in doc.get('covers', []) if cover != -1]