code: def toXMLFeed(self):
          
          feed = self.toXML()
  
          xml_header = '<?xml version="1.0" encoding="UTF-8"?>\n'
          return xml_header + feed.toprettyxml(indent='  ')
docs: Convert this cateen information into string
              which is a valid OpenMensa v2 xml feed
  
              :rtype: str