Curvature and Torsion from VMTK

Hi,
I have problems reading the code from the VMTK source code.
I am not sure if the curvature, torsion from the centerline property are calculated by averaging (SlicerExtension-VMTK/ExtractCenterline.py at e01c4fea8e67d45c646f7c66a1183063dd06bcbb · vmtk/SlicerExtension-VMTK · GitHub)? If so, since torsion has negative values, did they use the absolute value for averaging?
I also checked the code for the network property. It seems the curvature and torsion are the averages of all the points (SlicerExtension-VMTK/ExtractCenterline.py at e01c4fea8e67d45c646f7c66a1183063dd06bcbb · vmtk/SlicerExtension-VMTK · GitHub). How does the VMTK deal with torsion? Thank you for your help!
best,
Ge