Change Extents Using ParaView Python

Hello, I’ve been working at data wrangling a rather large data set (just under an exabyte) and am on my last bit of transformation to get it working for visualization on a smaller supercomputer. My problem is that I have a large pvti file whose z axis is actually time. I have some ParaView python code that extracts a volume of interest (VOI), a slice representing time, and saves that slice. My last problem is that the z value extents in the VOI is the z value and I’d like to make it zero. HOW do I (re)set the extent for a data set in ParaView Python? Below is a pertinent snippet of code where I would like to change the extents of the results of extractSubset1 before saving.
Thanks, --John.

extractSubset1 = ExtractSubset(registrationName='ExtractSubset1', Input=magOnepvti)
extractSubset1.VOI = [0, 45716, 0, 11400, 0, 0]
for i in range(0,799):
  extractSubset1.VOI = myVOI
  UpdatePipeline(time=0.0, proxy=extractSubset1)
  # here is where we would change the z value to 0 ...
  SaveData('/lustre/scratch4/turquoise/patchett/EQSIM/Experiment10/time-'+ str(i) +'/mag-'+ str(piece)+ '.pvti', proxy=extractSubset1, CellDataArrays=['mag'],