[SQLObject] Inheritance and MultipleJoin

[Luis J. P. <jav...@gm...>]

I'd like to know if there is a restriction using inheritance about
multiplejoin function because I'm getting an error and I don't know why.
I've the following code:

class Question(InheritableSQLObject):
    filename = StringCol(default=None, length=255, unique=True)
    title = StringCol(default=None)
    default_mark = FloatCol(default=0.0)
    wording = RelatedJoin('Content')
    term_questions = RelatedJoin('Term', joinColumn='term',
otherColumn='question',
                                 intermediateTable='Term_questions')
    answers = MultipleJoin('Answer')
    questionref = MultipleJoin('QuestionRef')


class Answer(SQLObject):
    value = StringCol(default=None)
    calification = FloatCol(default=None)
    ide = StringCol(default=None)
    question = ForeignKey('Question')


class Ord(Question):
    _inheritable = False
    shuffle = BoolCol()
    orderanswers = MultipleJoin('OrderChoice')


class OrderChoice(SQLObject):
    value = StringCol(default=None)
    ord = IntCol(default=None)
    ide = StringCol(default=None)
    question = ForeignKey('Ord')

and when I've a Ord instance (called 'q') and I do 'q.orderanswers' I get
the following error:

sqlobject.dberrors.OperationalError: Unknown column 'ord_id' in 'where
clause'

Any idea?

Thanks!!