code: def fromXml(xml):
          
          walkthrough = XWalkthrough(name=xml.get('name', ''),
                                     version=xml.get('version'))
          
          for xslide in xml:
              walkthrough.addSlide(XWalkthroughSlide.fromXml(xslide))
          
          return walkthrough
docs: Creates a new walkthrough element from XML
          
          :param      xml | <xml.etree.ElementTree.Element>
          
          :return     <XWalkthrough> || None