Save this message_sending object into an xml.dom.Element object.

def save_xml(self, doc, element):
        '''Save this message_sending object into an xml.dom.Element object.'''
        for cond in self._targets:
            new_element = doc.createElementNS(RTS_NS, RTS_NS_S + 'targets')
            new_element.setAttributeNS(XSI_NS, XSI_NS_S + 'type', 'rtsExt:condition_ext')
            cond.save_xml(doc, new_element)
            element.appendChild(new_element)