Creates a new walkthrough element from XML
        
        :param      xml | <xml.etree.ElementTree.Element>
        
        :return     <XWalkthrough> || None

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