docs: def save_xml(self, doc, element):
          '''Save this location into an xml.dom.Element object.'''
          element.setAttributeNS(RTS_EXT_NS, RTS_EXT_NS_S + 'x', str(self.x))
          element.setAttributeNS(RTS_EXT_NS, RTS_EXT_NS_S + 'y', str(self.y))
          element.setAttributeNS(RTS_EXT_NS, RTS_EXT_NS_S + 'height',
                                 str(self.height))
          element.setAttributeNS(RTS_EXT_NS, RTS_EXT_NS_S + 'width',
                                 str(self.width))
          element.setAttributeNS(RTS_EXT_NS, RTS_EXT_NS_S + 'direction',
                                 dir.to_string(self.direction).lower())