Updates the xml element contents to matches the instance contents.

        :returns: Updated XML element
        :rtype: lxml.etree._Element

def update_xml_element(self):
        """
        Updates the xml element contents to matches the instance contents.

        :returns: Updated XML element
        :rtype: lxml.etree._Element
        """

        if not hasattr(self, 'xml_element'):
            self.xml_element = etree.Element(self.name, nsmap=NSMAP)

        self.xml_element.clear()
        self.xml_element.set('id', self.id)

        for child in self.children:
            child.update_xml_element()
            self.xml_element.append(child.xml_element)

        return self.xml_element