необходимо узнать , что делает данный эндпоинт @app.route('/books_by_author', methods=['GET', 'POST']) def get_remains_books_by_author(): with session_factory() as session: if request.method == 'POST': author_id = request.form.get('author_id', type=int) result = session.execute(select(Book.count).filter_by(author_id=author_id)).all() remains_books = 0 for count in result: remains_books += count[0] return render_template( "show_remaining_books_by_author.html", count=remains_books, id=author_id)