code: def fromXml(xml):
          
          slide = XWalkthroughSlide(**xml.attrib)
          
          # create the items
          for xgraphic in xml:
              slide.addItem(XWalkthroughItem.fromXml(xgraphic))
          
          return slide
docs: Creates a new slide from XML.
          
          :return     <XWalkthroughSlide>