Using VMTK Branch Extractor Programatically (Python)

How can I get a bifurcated centerline as two separate numpy arrays? I can view the two centerlines with the below code. How can I then get the red centerline as one numpy array, and the blue centerline as another numpy array?

Thank you!

vmtkCommand = r'vmtkcenterlines -ifile ' + modelPath + r' --pipe vmtkbranchextractor -ofile ' + extractedPath + r' --pipe vmtkcenterlineviewer -cellarray CenterlineIds'
myPype = pypes.PypeRun(vmtkCommand)

Which returns:

You can see an example of how to extract a specific branch by thresholding based on group ID: