Assign the default values when updating a model

    This is done on fields with `on_update=<value>`.

def _from_rest_on_update(model, props):
    """ Assign the default values when updating a model

    This is done on fields with `on_update=<value>`.
    """

    fields = model.get_fields_with_prop('on_update')

    for field in fields:
        props[field[0]] = field[1]