'| Sets the shadow pen used to draw lines between points (this is for enhancing contrast or
emphacizing data).
| This line is drawn behind the primary pen (see :func:`setPen() <pyqtgraph.PlotDataItem.setPen>`)
and should generally be assigned greater width than the primary pen.
| *pen* can be a QPen or any argument accepted by :func:`pyqtgraph.mkPen() <pyqtgraph.mkPen>`'

def setShadowPen(self, *args, **kargs):

    pen = fn.mkPen(*args, **kargs)
    self.opts['shadowPen'] = pen
    self.updateItems()
