'Bump a question: trigger a write_date by writing on a dummy bump_date
field. One cannot bump a question more than once every 10 days.'

@api.multi
def bump(self):

    self.ensure_one()
    if (self.forum_id.allow_bump and (not self.child_ids) and ((datetime.today() - datetime.strptime(self.write_date, tools.DEFAULT_SERVER_DATETIME_FORMAT)).days > 9)):
        return self.sudo().write({'bump_date': fields.Datetime.now()})
    return False
