def _add_attribute(self, att, str):
        app_xml = xmlp.parse(self.fullpath+"/"+self.name+"-app.xml")
        root = app_xml.documentElement
        try:
            a = app_xml.getElementsByTagName(att)[0]
            app_xml.getElementsByTagName(att)[0].childNodes[0].data = str
        except:
            id = app_xml.createElement(att)
            node = app_xml.createTextNode(str)
            id.appendChild(node)
            root.appendChild(id)
        res = open(self.fullpath+"/"+self.name+"-app.xml", "w")
        res.writelines(app_xml.toprettyxml())
        res.close()

<id>
    blablabla
</id>

<id>blablabla</id>

        root = etree.Element("application", xmlns="http://ns.adobe.com/air/application/1.5")
        etree.SubElement(root, "id").text = id
        etree.SubElement(root, "version").text = version
        etree.SubElement(root, "filename").text = filename
        etree.SubElement(root, "name").text = self.name
        root.append(etree.XML(app_window))
        handle = etree.tostring(root, pretty_print=True, encoding='utf-8', xml_declaration=True)