Loads the XML text for a new walkthrough.
        
        :param      walkthrough | <XWalkthrough> || <str> || <xml.etree.ElementTree.Element>

def load(self, walkthrough):
        """
        Loads the XML text for a new walkthrough.
        
        :param      walkthrough | <XWalkthrough> || <str> || <xml.etree.ElementTree.Element>
        """
        if type(walkthrough) in (str, unicode):
            walkthrough = XWalkthrough.load(walkthrough)
        
        self.setUpdatesEnabled(False)
        self.clear()
        for slide in walkthrough.slides():
            self.addSlide(slide)
        self.setUpdatesEnabled(True)
        self.updateUi()