Sets the pen that will be used when drawing the grid lines.
        
        :param      gridPen | <QtGui.QPen> || <QtGui.QColor>

def setGridPen( self, gridPen ):
        """
        Sets the pen that will be used when drawing the grid lines.
        
        :param      gridPen | <QtGui.QPen> || <QtGui.QColor>
        """
        delegate = self.itemDelegate()
        if ( isinstance(delegate, XTreeWidgetDelegate) ):
            delegate.setGridPen(gridPen)