flask 的relationship使用

#一对多 学生是一 (一个学生有多本书)
class Student(db.Model):
 __tablename__ = "student"
 id = db.Column(db.Integer,primary_key=True)
 name = db.Column(db.String(200))
 age = db.Column(db.String(200))
 gender = db.Column(db.String(200))
 #设置relations
 books = db.relationship("Book",backref = "students")

#一对多 书是多 (一个学生有多本书)
class Book(db.Model):
 __tablename__ = "book"
 id = db.Column(db.Integer,primary_key=True)
 book_name = db.Column(db.String(200))
 author = db.Column(db.String(200))
 publish = db.Column(db.String(200))
 price = db.Column(db.String(200))
 types = db.Column(db.String(200))
 pages = db.Column(db.String(200))
 s_id = db.Column(db.Integer,db.ForeignKey(Student.id))

@app.route("/home")
def home():
 #所有的学生
 s_all = Student.query.all()
 return render_template("hh.html",s_all=s_all)

<form action="">
 <table border="1px">
 <a href="{{url_for('insert')}}">新增</a>

 {% for s in s_all%}

<!--        当前学生有哪些书籍 通过relationship-->
 {% for b in s.books %}
 <tr>
 <td>{{s.name}}</td>
 <td>{{b.book_name}}</td>
 <td>{{b.author}}</td>
 <td>{{b.publish}}</td>
 <td>{{b.price}}</td>
 <td>{{b.types}}</td>
 <td>{{b.pages}}</td>
 <td>{{s.id}}</td>
 <td>{{b.s_id}}</td>
 <td><a href="{{url_for('delete',id = b.id)}}">删除</a></td>
 </tr>
 {% endfor %}
 {% endfor %}

 </table>
</form>