def METHOD_NAME(self,in_vector0,in_vector1):
    vector0 = [in_vector0[0], in_vector0[1], in_vector0[2]]
    vector1 = [in_vector1[0], in_vector1[1], in_vector1[2]]
    vtk.vtkMath.Normalize(vector0)
    vtk.vtkMath.Normalize(vector1)
    sum = [
        vector0[0] + vector1[0],
        vector0[1] + vector1[1],
        vector0[2] + vector1[2]]
    difference = [
        vector0[0] - vector1[0],
        vector0[1] - vector1[1],
        vector0[2] - vector1[2]]
    sumNorm = vtk.vtkMath.Norm(sum)
    differenceNorm = vtk.vtkMath.Norm(difference)