code: def addGaussNoise(self, sigma):
          
          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
docs: 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()