I rewrite a function called default_get

class open_questionnaire_line(osv.osv_memory):
    _name = 'open.questionnaire.line'
    _rec_name = 'question_id'
    _columns = {
        'question_id': fields.many2one('crm_profiling.question','Question', required=True),
        'answer_id': fields.many2one('crm_profiling.answer', 'Answer'),
        'wizard_id': fields.many2one('open.questionnaire', 'Questionnaire'),
    }


class open_questionnaire(osv.osv_memory):
    _name = 'open.questionnaire'
    _columns = {
        'questionnaire_id': fields.many2one('crm_profiling.questionnaire', 'Questionnaire name'),
        'question_ans_ids': fields.one2many('open.questionnaire.line', 'wizard_id', 'Question / Answers'),
    }

    def default_get(self, cr, uid, fields, context=None):
        if context is None: context = {}
        res = super(open_questionnaire, self).default_get(cr, uid, fields, context=context)
        questionnaire_id = context.get('questionnaire_id', False)
        if questionnaire_id and 'question_ans_ids' in fields:
            query = """
                select question as question_id from profile_questionnaire_quest_rel where questionnaire = %s"""
            cr.execute(query, (questionnaire_id,))
            result = cr.dictfetchall()
            res.update(question_ans_ids=result)
        return res

and in my view

 <record id="open_questionnaire_form" model="ir.ui.view">
            <field name="name">open.questionnaire.form</field>
            <field name="model">open.questionnaire</field>
            <field name="arch" type="xml">
                <form string="Open Questionnaire">
                    <separator colspan="4" string="Questionnaire"/>
                    <field name="question_ans_ids" colspan="4" nolabel="1" mode="tree" width="550" height="200"/>
                    <footer>
                        <button name="questionnaire_compute" string="Save Data" type="object" class="oe_highlight"/>
                        or
                        <button string="Cancel" class="oe_link" special="cancel" />
                    </footer>
                </form>
            </field>
        </record>

But it gives me an error

Error: send_commands to 'question_ans_ids' receive a non command value.

[{"question_id":4},{"question_id":3},{"question_id":2},{"question_id":1}]

How can I overcome this error.

Note : This module is the exact copy of crm_profiling (working in v8 and available only for v8). But now I trying it to rewrite in v9.

Please help