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%.

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)