@api.multi
def action_undo_history(self):
    history_obj = self.env['membership.history']

    for reg in self:
        history_ids = history_obj.search([('name_id', '=', reg.name_id.id)], history_ids[0].date)
        history_ids = self.env['membership.history'].search([('name_id', '=', reg.name_id.id)], order='date desc')

        current_state = reg.name_id.state
        history_state = reg.state_new

        if history_ids[0] == reg and current_state == history_state:
            reg.name_id.state == reg.state_old

        else :
            message = _("Only the latest history can be cancelled !")
            mess= {
            'title': _('Error : Cancelling State'),
            'message' : message
            }
return {'warning': mess}