def METHOD_NAME(self):
    """Get the active curve, add 1 to all y values, use this new y
    array to replace the original curve"""
    # By inheriting from PlotAction, we get access to attribute self.plot
    # which is a reference to the PlotWindow
    activeCurve = self.plot.getActiveCurve()
    if activeCurve is None:
        qt.QMessageBox.information(self.plot,
                                   'Shift Curve',
                                   'Please select a curve.')
    else:
        # Unpack curve data.
        # Each curve is represented by an object with methods to access:
        # the curve data, its legend, associated information and curve style
        # Here we retrieve the x and y data of the curve
        x0 = activeCurve.getXData()
        y0 = activeCurve.getYData()
        # Add 1 to all values in the y array
        # and assign the result to a new array y1
        y1 = y0 + 1.0
        # Set the active curve data with the shifted y values
        activeCurve.setData(x0, y1)