Python Flask 解决form.validate_on_submit()总是为false的问题

# 表单类：
class Form(FlaskForm):
    username = StringField("用户名：", validators=[DataRequired()])
    phone = IntegerField("手机号：", validators=[DataRequired()])
    email = StringField("邮箱：", validators=[DataRequired(),email("Email ERROR")])
    age = IntegerField("年龄：", validators=[DataRequired()])
    about = TextAreaField("关于我：", validators=[DataRequired()])
    submit = SubmitField("注册")
    password = PasswordField("密码：", validators=[DataRequired()])
    confirm = PasswordField("确定密码：", validators=[DataRequired()])

# 视图函数：
@app.route("/",methods=["GET","POST"])
def index():
    form=Form()
    print(form.validate_on_submit())
    if form.validate_on_submit():
        return redirect(url_for("suc"))
    else:
        return render_template("register2.html",form=form)

@app.route("/suc")
def suc():
    return "SUCCESS"

 HTML代码：

<form method="post">
    <div class="form-group">