'Set the curves to fill between.
Arguments must be instances of PlotDataItem or PlotCurveItem.
Added in version 0.9.9'

def setCurves(self, curve1, curve2):

    if (self.curves is not None):
        for c in self.curves:
            try:
                c.sigPlotChanged.disconnect(self.curveChanged)
            except (TypeError, RuntimeError):
                pass
    curves = [curve1, curve2]
    for c in curves:
        if ((not isinstance(c, PlotDataItem)) and (not isinstance(c, PlotCurveItem))):
            raise TypeError('Curves    must    be    PlotDataItem    or    PlotCurveItem.')
    self.curves = curves
    curve1.sigPlotChanged.connect(self.curveChanged)
    curve2.sigPlotChanged.connect(self.curveChanged)
    self.setZValue((min(curve1.zValue(), curve2.zValue()) - 1))
    self.curveChanged()
