The changes of dictionary property cannot save to db.

[chyulin]

When I set a dict cast to a model, any changes of dict property doesn't affect the real value.
And can't save the change to db.

class Test(Model):

    __table__ = 'test'
    __casts__ = {
        'json_field': 'dict'
    }


test_obj = Test.find(1)
test_obj.json_field['new_data'] = 1   # update json_field
test_obj.save()  # nothing happened