Overloaded from the base QGraphicsScene class to set the modified \
        state for this scene to being modified.
                    
        :param      item        <QGraphicsItem>
        
        :return     <bool> success

def addItem( self, item ):
        """
        Overloaded from the base QGraphicsScene class to set the modified \
        state for this scene to being modified.
                    
        :param      item        <QGraphicsItem>
        
        :return     <bool> success
        """
        result = super(XNodeScene, self).addItem(item)
        self.setModified()
        self._cache.add(item)
        
        return result