class XfaTreeNode extends FormTreeNode implements OutputStreamResource {

    /**
     * Start sequence of an artificial boundary between XFA fragments added by RUPS
     */
    public static final byte[] BOUNDARY_START = "<!--\nRUPS XFA individual packet: end of [".getBytes();
    /**
     * Middle sequence of an artificial boundary between XFA fragments added by RUPS
     */
    public static final byte[] BOUNDARY_MIDDLE = "]; start of [".getBytes();
    /**
     * End sequence of an artificial boundary between XFA fragments added by RUPS
     */
    public static final byte[] BOUNDARY_END = "]\n-->".getBytes();
    /**
     * A serial version UID.
     */
    private static final long serialVersionUID = 2463297568233643790L;

    /**
     * Creates the root node of the XFA tree. This will be a child of the FormTree root node.
     *
     * @param xfa the XFA node in the PdfTree (a child of the AcroForm node in the PDF catalog)
     */
    public XfaTreeNode(PdfObjectTreeNode xfa) {
        super(xfa);
    }

    /**
     * Writes (part of) the XFA resource to an OutputStream. If key is <code>null</code>, the complete resource is
     * written; if key refers to an individual package, this package only is written to the OutputStream.
     *
     * @param os the OutputStream to which the XML is written.
     * @throws IOException usual exception when there's a problem writing to an OutputStream
     */
    public void writeTo(OutputStream os) throws IOException {<FILL_FUNCTION_BODY>}

    /**
     * Adds a child node to the XFA root. The child node either corresponds with the complete XDP stream (if the XFA
     * root only has one child) or with individual packet.
     *
     * @param key   the name of the packet
     * @param value the corresponding stream node in the PdfTree
     */
    public void addPacket(String key, PdfObjectTreeNode value) {
        FormTreeNode node = new FormTreeNode(value);
        node.setUserObject(key);
        this.add(node);
    }

}

        Enumeration children = this.children();
        FormTreeNode node;
        PRStream stream;
        String key = null;
        String tmp = null;
        while (children.hasMoreElements()) {
            node = (FormTreeNode) children.nextElement();
            if (key != null) {
                os.write(BOUNDARY_START);
                os.write(key.getBytes());
                os.write(BOUNDARY_MIDDLE);
                tmp = (String) node.getUserObject();
                os.write(tmp.getBytes());
                os.write(BOUNDARY_END);
            }
            key = tmp;
            stream = (PRStream) node.getCorrespondingPdfObjectNode().getPdfObject();
            os.write(PdfReader.getStreamBytes(stream));
        }
        os.flush();
        os.close();
    
<methods>public void <init>() ,public void <init>(com.lowagie.rups.view.itext.treenodes.PdfObjectTreeNode) ,public com.lowagie.rups.view.itext.treenodes.PdfObjectTreeNode getCorrespondingPdfObjectNode() <variables>protected com.lowagie.rups.view.itext.treenodes.PdfObjectTreeNode object_node,private static final long serialVersionUID