private function buildExtensions(SimpleXMLElement $phpDocumentor): array
    {
        if ((array) $phpDocumentor->parser === []) {
            return $this->extensions;
        }

        if ((array) $phpDocumentor->parser->extensions === []) {
            return $this->extensions;
        }

        return $this->buildArrayFromNode($phpDocumentor->parser->extensions);
    }