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Solve the following problem using Python, implementing the functions described below, one line at a time
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<USER_TASK:>
Description:
 def update_question(self, question_form):
 """Updates an existing question. arg: question_form (osid.assessment.QuestionForm):
 the form containing the elements to be updated raise: IllegalState - ``question_form`` already used in an update transaction raise: InvalidArgument - the form contains an invalid value raise: NullArgument - ``question_form`` is ``null`` raise: OperationFailed - unable to complete request raise: PermissionDenied - authorization failure occurred raise: Unsupported - ``question_form`` did not originate from ``get_question_form_for_update()`` *compliance: mandatory -- This method must be implemented.* """

        collection = JSONClientValidated('assessment',
                                         collection='Item',
                                         runtime=self._runtime)
        if not isinstance(question_form, ABCQuestionForm):
            raise errors.InvalidArgument('argument type is not an QuestionForm')
        if not question_form.is_for_update():
            raise errors.InvalidArgument('the QuestionForm is for update only, not create')
        try:
            if self._forms[question_form.get_id().get_identifier()] == UPDATED:
                raise errors.IllegalState('question_form already used in an update transaction')
        except KeyError:
            raise errors.Unsupported('question_form did not originate from this session')
        if not question_form.is_valid():
            raise errors.InvalidArgument('one or more of the form elements is invalid')
        item_id = Id(question_form._my_map['itemId']).get_identifier()
        item = collection.find_one({'$and': [{'_id': ObjectId(item_id)},
                                   {'assigned' + self._catalog_name + 'Ids': {'$in': [str(self._catalog_id)]}}]})
        item['question'] = question_form._my_map
        try:
            collection.save(item)
        except:  # what exceptions does mongodb save raise?
            raise errors.OperationFailed()
        self._forms[question_form.get_id().get_identifier()] = UPDATED
        # Note: this is out of spec. The OSIDs don't require an object to be returned:
        return objects.Question(osid_object_map=question_form._my_map,
                                runtime=self._runtime,
                                proxy=self._proxy)