}
            List<Server> servers = settings.getServers();
            for (int i = 0; i < servers.size(); i++) {
                Server server = servers.get(i);
                String serverField = "servers.server[" + i + "]";
                validateStringEmpty(problems, serverField + ".username", server.getUsername(), msgS);

        ExtensionDescriptor extensionDescriptor = new ExtensionDescriptor();

        XmlNode dom;
        try {
            XMLStreamReader reader = WstxInputFactory.newFactory().createXMLStreamReader(is);
            dom = XmlNodeStaxBuilder.build(reader);
        } catch (XMLStreamException e) {
            throw new IOException(e.getMessage(), e);
        }

        if (!"extension".equals(dom.getName())) {

        Path path = request.getPath();
        URL url = request.getURL();
        Reader reader = request.getReader();
        InputStream inputStream = request.getInputStream();
        if (path == null && url == null && reader == null && inputStream == null) {
            throw new IllegalArgumentException("path, url, reader or inputStream must be non null");
        }
        try {

     *
     * @return The identifier of the model from which the problem originated or an empty string if unknown, never
     *         {@code null}.
     */
    String getModelId();

    /**
     * Gets the applicable maven version/validation level of this problem
     * @return The version, never {@code null}.
     */
    Version getVersion();

    /**
     * Creates a user-friendly source hint for the specified model.
     *
     * @param model The model to create a source hint for, may be {@code null}.
     * @return The user-friendly source hint, never {@code null}.
     */
    static String toSourceHint(Model model) {
        if (model == null) {
            return "";
        }

        StringBuilder buffer = new StringBuilder(128);

    }

    private static XmlNode toXmlNode(Reader reader) throws XMLStreamException, IOException {
        return toXmlNode(reader, null);
    }

    private static XmlNode toXmlNode(Reader reader, XmlNodeStaxBuilder.InputLocationBuilderStax locationBuilder)
            throws XMLStreamException, IOException {
        return XmlNodeStaxBuilder.build(reader, locationBuilder);
    }

    }

    @Override
    public File findArtifact(Artifact artifact) {
        requireNonNull(artifact, "artifact cannot be null");
        File file = null;

        for (WorkspaceReader reader : readers) {
            file = reader.findArtifact(artifact);
            if (file != null) {
                break;
            }
        }

        return file;
    }

    @Override

     * @return The deserialized model, never {@code null}.
     * @throws IOException If the model could not be deserialized.
     * @throws ModelParseException If the input format could not be parsed.
     */
    Model read(Path input, Map<String, ?> options) throws IOException, ModelParseException;

    /**
     * Reads the model from the specified character reader. The reader will be automatically closed before the method

     */
    public String getModelId() {
        if (result == null || result.getModelIds().isEmpty()) {
            return "";
        }
        return result.getModelIds().get(0);
    }

    /**
     * Gets the problems that caused this exception.
     *
     * @return The problems that caused this exception, never {@code null}.
     */

     * @param session The repository session, must not be {@code null}.
     * @param artifactCoordinate The artifact coordinate for which the version needs to be resolved, must not be {@code null}
     * @return The version result, never {@code null}.
     * @throws VersionResolverException If the metaversion could not be resolved.
     */
    @Nonnull