oldExtension.setGroupId(extension.getGroupId());
        oldExtension.setArtifactId(extension.getArtifactId());
        oldExtension.setVersion(extension.getVersion());
        if (extension.getClassLoadingStrategy() != null) {
            oldExtension.setClassLoadingStrategy(extension.getClassLoadingStrategy());
        }
        this.extension = oldExtension;
    }

    public CoreExtension getExtension() {
        return extension;

                IllegalArgumentException.class, () -> rtInfo.isMavenVersion(""), "Bad version range wasn't rejected");

        assertThrows(
                NullPointerException.class, () -> rtInfo.isMavenVersion(null), "Bad version range wasn't rejected");
    }

                .findAny()
                .orElseThrow(() -> new LookupException("No service of type " + type));
    }

    @Override
    public <T> T lookup(Class<T> type, String name) {
        return null;
    }

    @Override
    public <T> Optional<T> lookupOptional(Class<T> type) {
        return Optional.empty();
    }

    @Override
    public <T> Optional<T> lookupOptional(Class<T> type, String name) {

                            "schema": {
                                "anyOf": [
                                    {"type": "string", "pattern": "^fixedquery$"},
                                    {"type": "null"},
                                ],
                                "title": "Q",
                            },
                        }
                    ],
                    "responses": {

<div class="screenshot">
<img src="/img/tutorial/separate-openapi-schemas/image02.png">
</div>

This means that it will **always have a value**, it's just that sometimes the value could be `None` (or `null` in JSON).

    }

    @Override
    public void error(String msg, Throwable t) {
        error(msg);

        if (null != t) {
            t.printStackTrace(out);
        }
    }

    //
    // Don't need any of this
    //
    @Override
    public String getName() {
        return null;
    }

    @Override
    public boolean isTraceEnabled() {
        return false;
    }

    @Override

Note that objects with `null` versions, i.e. objects created prior to enabling versioning break the immutability guarantees provided by versioning. When existing object replication is enabled, these objects will be replicated as `null` versions to the remote targets provided they are not present on the target or if `null` version of object on source is newer than the `null` version of object on target.

        try (InputStream is = getClass().getResourceAsStream("/xml/pom.xml")) {
            model = new MavenXpp3Reader().read(is);
        }

        // Serialize an inner child here so that the BaseObject.childrenTracking is non null
        Build build = model.getBuild();

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try (ObjectOutputStream oos = new ObjectOutputStream(baos)) {
            oos.writeObject(build);
        }

 *     public Collection<Type> provides() {
 *         return Arrays.asList(
 *             type("kotlin-library", "jar", "kotlin"),
 *             type("docker-image", "tar.gz", null)
 *         );
 *     }
 * }
 * </pre>
 *
 * @see org.apache.maven.api.Type
 * @see org.apache.maven.api.spi.ExtensibleEnumProvider
 * @since 4.0.0
 */
@Experimental
@Consumer
@Named

            <label>Message: <input type="text" id="messageText" autocomplete="off"/></label>
            <button>Send</button>
        </form>
        <ul id='messages'>
        </ul>
        <script>
        var ws = null;
            function connect(event) {
                var itemId = document.getElementById("itemId")
                var token = document.getElementById("token")