public function get($uid)
    {
        if ($uid <= 0) {
            throw new \InvalidArgumentException('$uid must be > 0.', 1331488761);
        }

        if (!isset($this->items[$uid])) {
            throw new \Tx_Oelib_Exception_NotFound(
                'This map currently does not contain a model with the UID ' .
                $uid . '.'
            );
        }

        return $this->items[$uid];
    }