How to save model by using the ruby bindings

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Hi I want to modify a openstudio model in command prompt by ruby bindings. I want to load the model and then assign a a thermal zone to a HVAC loop.

require 'OpenStudio'

translator = OpenStudio::OSVersion::VersionTranslator.new
path = OpenStudio::Path.new('model.osm')
model = translator.loadModel(path).get
hVACs = model.getAirLoopHVACs[0]

floor = model.getBuildingStorys[1]

hVACs .addBranchForZone(floor.spaces[1].thermalZone.get)

I get a True for addBranchForZone, but when I open the model in openstudio, the zone wasn't assigend to that air loop. I suppose the model haven't be save yet, but I'm not sure there have save function in ruby bindings

Any advice and suggestion, or any tutorial or introduction or documentation about openstudio ruby binding would be appreciated!