'Unpacks a student response value submitted as JSON.'

def _unpack(self, json_value):

    json_d = json.loads(json_value)
    if (not isinstance(json_d, dict)):
        json_d = {}
    comment_value = json_d.get('comment', '')
    if (not isinstance(json_d, basestring)):
        comment_value = ''
    options_value = json_d.get('options', [])
    if (not isinstance(options_value, list)):
        options_value = []
    return {'options_value': options_value, 'comment_value': comment_value}
