Returns the ID of the Logout Request
        :param request: Logout Request Message
        :type request: string|DOMDocument
        :return: string ID
        :rtype: str object

def get_id(request):
        """
        Returns the ID of the Logout Request
        :param request: Logout Request Message
        :type request: string|DOMDocument
        :return: string ID
        :rtype: str object
        """
        if isinstance(request, etree._Element):
            elem = request
        else:
            if isinstance(request, Document):
                request = request.toxml()
            elem = fromstring(request, forbid_dtd=True)
        return elem.get('ID', None)