Merge CT volume node with a model node in python

hey, i found have this from the nightly script repository

meshVolumeNode = getNode(mesh_model)
seg = slicer.mrmlScene.AddNewNodeByClass(‘vtkMRMLSegmentationNode’)
slicer.modules.segmentations.logic().ImportModelToSegmentationNode(meshVolumeNode, seg)
seg.CreateClosedSurfaceRepresentation()
slicer.mrmlScene.RemoveNode(meshVolumeNode)

once i have a segment volume node, how can i merge it with a CT volume node?
also what is the function SetAndObserveImageData used for? the VTK documentation doesn’t explain much.

I’m working on an extension that builds around panoramic reconstruction which essentially straightens a volume: Slice rotation in viewport when using SetSliceToRASByNTP in python - #2 by lassoan
but i also want this reconstruction to incorporate mesh models so im trying to merge volumes - im not sure if this is the correct approach to this.

thanks!