public function convert($source)
    {
        $indices = [];

        $xpath = new \DOMXPath($source);
        $indexSearchPath = sprintf("/%s/%s", self::ROOT_NODE_NAME, self::INDEX_NODE_TYPE);

        foreach ($xpath->query($indexSearchPath) as $indexNode) {
            $indexIdentifier = $indexNode->getAttribute('identifier');
            $indices[$indexIdentifier] = $this->parseIndexConfig($xpath, $indexNode);
        }

        return $indices;
    }