Has Centerline from Extract centreline module be smoothed?

I want to do the geometric analysis. The VMTK tutorial described that the centerline goes through a Laplacian smoothing filter first and then computes the derivatives and the related quantities (Geometric Analysis | vmtk - the Vascular Modelling Toolkit). I did not found the smoothing in the ExtractCenterline.py (SlicerExtension-VMTK/ExtractCenterline.py at master · vmtk/SlicerExtension-VMTK · GitHub)
I am not sure if I understand the code well. Could you give me some advice?
Thank you so much!
Ge Tang