change form type flask from text to selection flask admin

1   class MyModel(db.Model):
2       id = db.Column(db.Integer, primary_key=True)
3       my_field = db.Column(db.String(128))  # Field I would like to be choices
4
5
6    class MyModelView(ModelView):
7        """
8        Admin manager for MyModel
9        """
10
11            form_choices = {
12                 'my_field': [
13                     ('choice_1', 'Choice 1'),
14                     ('choice_2', 'Choice 2'),
15                     ('choice_3', 'Choice 3'),
16                     ('choice_4', 'Choice 4'),
17                     ('choice_5', 'Choice 5')
18                ]
19           }
20
21        def __init__(self):
22            super(MyModelView, self).__init__(MyModel, db.session)
23