code: def gradient(self):
          
          gradFill = self._xPr.get_or_change_to_gradFill()
          self._fill = _GradFill(gradFill)
docs: 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%.