public function showUsers($limit = null, $offset = null, $filters = null, $order = null)
    {

        if ($limit!= null && $limit < 1) {
            throw new InvalidArgumentException(
                "Api::who() limit must be a min 1 ");
        }
        if ($offset!= null && $offset < 0) {
            throw new InvalidArgumentException(
                "Api::who offset must be a positive number,  min 0 ");
        }

        $command = $this->client->getCommand('Who', array('limit' => $limit,'offset'=>$offset, 'filters' => $filters, 'order' => $order));

        return $this->executeCommand($command);
    }