Paints this item to the system.
        
        :param      painter | <QPainter>
                    option  | <QStyleOptionGraphicItem>
                    widget  | <QWidget>

def paint( self, painter, option, widget ):
        """
        Paints this item to the system.
        
        :param      painter | <QPainter>
                    option  | <QStyleOptionGraphicItem>
                    widget  | <QWidget>
        """
        style       = self.itemStyle()
        ItemStyle   = self.treeItem().ItemStyle
        
        if ( style == ItemStyle.Group ):
            self.paintGroup( painter )
        
        elif ( style == ItemStyle.Milestone ):
            self.paintMilestone( painter )
        
        else:
            self.paintNormal( painter )