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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def gradient(self):
 """Sets the fill type to gradient. If the fill is not already a gradient, a default gradient is added. The default gradient corresponds to the default in the built-in PowerPoint "White" template. This gradient is linear at angle 90-degrees (upward), with two stops. The first stop is Accent-1 with tint 100%, shade 100%, and satMod 130%. The second stop is Accent-1 with tint 50%, shade 100%, and satMod 350%. """

        gradFill = self._xPr.get_or_change_to_gradFill()
        self._fill = _GradFill(gradFill)