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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 addGaussNoise(self, sigma):
 """ Add gaussian noise. :param float sigma: sigma is expressed in percent of the diagonal size of actor. :Example: .. code-block:: python from vtkplotter import Sphere Sphere().addGaussNoise(1.0).show() """

        sz = self.diagonalSize()
        pts = self.coordinates()
        n = len(pts)
        ns = np.random.randn(n, 3) * sigma * sz / 100
        vpts = vtk.vtkPoints()
        vpts.SetNumberOfPoints(n)
        vpts.SetData(numpy_to_vtk(pts + ns, deep=True))
        self.poly.SetPoints(vpts)
        self.poly.GetPoints().Modified()
        return self