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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 extractSurface(image, radius=0.5):
 """ ``vtkExtractSurface`` filter. Input is a ``vtkImageData``. Generate zero-crossing isosurface from truncated signed distance volume. """

    fe = vtk.vtkExtractSurface()
    fe.SetInputData(image)
    fe.SetRadius(radius)
    fe.Update()
    return Actor(fe.GetOutput())