<configuration>
          <defaults><!-- equivalent to combine.children="merge" combine.self="merge" -->
            <!-- merge the content of the configuration element according to element name -->
            <parent>child</parent>
            <child>child</child>
            <parent-only>parent</parent-only>
          </defaults>
          <appends combine.children="append">
            <parent-only>parent</parent-only>

    /**
     * {@link NodeList}の文字列表現を追加します。
     *
     * @param children
     *            子要素。{@literal null}であってはいけません
     * @param buf
     *            文字列バッファ。{@literal null}であってはいけません
     */
    public static void appendChildren(final NodeList children, final StringBuilder buf) {
        assertArgumentNotNull("children", children);
        assertArgumentNotNull("buf", buf);

    private void wrapContentInContainer(Document document) {
        // Wrap the page in a text container to get the margins
        Elements bodyContent = document.body().children().remove();
        document.body().prepend("<div class='container'/>");
        document.body().children().get(0).html(bodyContent.outerHtml());
    }

    private void addTOC(Document document) {

    }

    private List<MavenProject> getChildProjects(MavenProject parent, MavenExecutionRequest request) {
        final List<MavenProject> children = parent.getCollectedProjects();
        if (children != null && request.isRecursive()) {
            return children;
        } else {
            return new ArrayList<>();
        }
    }

    private Optional<MavenProject> findOptionalProjectBySelector(

            # no idea why, so, let's just modify the existing one
            # new_section = Section(title=new_title, children=new_children)
            item.title = new_title
            item.children = new_children
            new_items.append(item)
        else:
            new_items.append(item)
    return new_items


def on_nav(

     */
    @Nonnull
    List<ModelProblem> getProblems();

    /**
     * Gets the children of this result.
     *
     * @return the children of this result, can be empty but never {@code null}
     */
    @Nonnull
    List<? extends ModelBuilderResult> getChildren();

    /**

                props.put(propertyDoc.getName(), propertyDoc.forClass(classDoc, additionalValues.values()));
            }
        }

        for (Element row : children(classDoc.getPropertiesTable(), "tr")) {
            List<Element> cells = children(row, "td");
            if (cells.size() != header.size()) {
                throw new RuntimeException(String.format("Expected %s <td> elements in <tr>, found: %s", header.size(), tr));

            List<XmlNode> children = new ArrayList<>();
            for (PlexusConfiguration c : config.getChildren()) {
                children.add(toXml(c, evaluator));
            }
            String name = config.getName();
            Object value = evaluator.evaluate(config.getValue());
            return new XmlNodeImpl(name, value != null ? value.toString() : null, null, children, null);
        }
    }

 */
@Experimental
@ThreadSafe
@Immutable
public interface XmlNode {

    String CHILDREN_COMBINATION_MODE_ATTRIBUTE = "combine.children";

    String CHILDREN_COMBINATION_MERGE = "merge";

    String CHILDREN_COMBINATION_APPEND = "append";

    /**
     * This default mode for combining children DOMs during merge means that where element names match, the process will

     */
    public void build(ClassDoc classDoc) {
        Set<String> signatures = new HashSet<String>();

        for (Element tr : children(classDoc.getMethodsTable(), "tr")) {
            List<Element> cells = children(tr, "td");
            if (cells.size() != 1) {
                throw new RuntimeException(String.format("Expected 1 cell in <tr>, found: %s", tr));
            }