public function findAll()
    {

        // query whether or not we've already loaded the value
        if (!isset($this->cache[__METHOD__])) {
            // try to load the link types
            $this->linkTypeStmt->execute();

            // initialize the array for the link types
            $linkTypes = array();

            // load the available link types
            $availableLinkTypes = $this->linkTypeStmt->fetchAll(\PDO::FETCH_ASSOC);

            // prepare the link types => we need the code as key
            foreach ($availableLinkTypes as $linkType) {
                $linkTypes[$linkType[MemberNames::CODE]] = $linkType;
            }

            // append the link types to the cache
            $this->cache[__METHOD__] = $linkTypes;
        }

        // return the link types from the cache
        return $this->cache[__METHOD__];
    }