* implement it:
 *
 * <pre>{@code
 * // won't work
 * TreeTraverser<NodeType> traverser = node -> node.getChildNodes();
 * }</pre>
 *
 * Instead, you can pass a lambda expression to the {@code using} factory method:
 *
 * <pre>{@code
 * TreeTraverser<NodeType> traverser = TreeTraverser.using(node -> node.getChildNodes());
 * }</pre>
 *
 * @author Louis Wasserman
 * @since 15.0

        return buf.toString().trim();
    }

    protected void parseTextContent(final Node node, final StringBuilder buf) {
        if (node.hasChildNodes()) {
            final NodeList nodeList = node.getChildNodes();
            for (int i = 0; i < nodeList.getLength(); i++) {
                final Node childNode = nodeList.item(i);
                parseTextContent(childNode, buf);
            }

        final String tag = element.getTagName();
        buf.append('<');
        buf.append(tag);
        appendAttrs(element.getAttributes(), buf);
        buf.append('>');
        appendChildren(element.getChildNodes(), buf);
        buf.append("</");
        buf.append(tag);
        buf.append('>');
    }

    /**
     * {@link NodeList}の文字列表現を追加します。
     *
     * @param children

            final NodeList snapshotNodeList = doc.getElementsByTagName("snapshot");
            if (snapshotNodeList.getLength() > 0) {
                final NodeList nodeList = snapshotNodeList.item(0).getChildNodes();
                for (int i = 0; i < nodeList.getLength(); i++) {
                    final Node node = nodeList.item(i);
                    if ("timestamp".equalsIgnoreCase(node.getNodeName())) {