Save this preceding condition into an xml.dom.Element object.

def save_xml(self, doc, element):
        '''Save this preceding condition into an xml.dom.Element object.'''
        super(Preceding, self).save_xml(doc, element)
        pre_element = doc.createElementNS(RTS_NS, RTS_NS_S + 'Preceding')
        if self.timeout:
            pre_element.setAttributeNS(RTS_NS, RTS_NS_S + 'timeout',
                    str(self.timeout))
        if self.sending_timing:
            pre_element.setAttributeNS(RTS_NS, RTS_NS_S + 'sendingTiming',
                                   self.sending_timing)
        for pc in self._preceding_components:
            new_element = doc.createElementNS(RTS_NS,
                                              RTS_NS_S + 'PrecedingComponents')
            pc.save_xml(doc, new_element)
            pre_element.appendChild(new_element)
        element.appendChild(pre_element)