flask-admin.py

group_user_relation = db.Table(
    'group_user_relation',
    db.Column('group_id', db.Integer, db.ForeignKey('group.id')),
    db.Column('user_id', db.Integer, db.ForeignKey('user.id'))
)


class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), unique=True)

    def __repr__(self):
        return str(self.username)


class Group(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(64), unique=True)
    users = db.relationship('User', secondary=group_user_relation)


admin = Admin(app, name='Admin', template_mode='bootstrap3')
admin.add_view(ModelView(User, db.session))
admin.add_view(ModelView(Group, db.session))
db.create_all()