flask渲染模板时报错TypeError: 'UnboundField' object is not callable

渲染模板时，访问页面提示TypeError: 'UnboundField' object is not callable

检查代码，发现实例化表单类是，没有加括号：form = NewNoteForm，加了括号后就解决了form = NewNoteForm()

@app.route('/index')
def index():
    form = NewNoteForm
    notes = Note.query.all()
    return render_template('index.html', notes=notes, form=form)