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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 alignLandmarks(source, target, rigid=False):
 """ Find best matching of source points towards target in the mean least square sense, in one single step. """

    lmt = vtk.vtkLandmarkTransform()
    ss = source.polydata().GetPoints()
    st = target.polydata().GetPoints()
    if source.N() != target.N():
        vc.printc('~times Error in alignLandmarks(): Source and Target with != nr of points!',
                  source.N(), target.N(), c=1)
        exit()
    lmt.SetSourceLandmarks(ss)
    lmt.SetTargetLandmarks(st)
    if rigid:
        lmt.SetModeToRigidBody()
    lmt.Update()
    tf = vtk.vtkTransformPolyDataFilter()
    tf.SetInputData(source.polydata())
    tf.SetTransform(lmt)
    tf.Update()
    actor = Actor(tf.GetOutput())
    actor.info["transform"] = lmt
    pr = vtk.vtkProperty()
    pr.DeepCopy(source.GetProperty())
    actor.SetProperty(pr)
    return actor