How do I store a camera visibility value into a user variable for Renderman in Katana?

Question

I have this short piece of code that modifies the attribute that I want. I can modify it but what I really want is to read it and save it into a user variable so that I can evaluate whether the visibility is 'on' or 'off'.

Interface.SetAttr("prmanStatements.attributes.visibility.camera", IntAttribute(0))

As it stands, that line of code turns off the camera visibility. But when trying to read the value of the same parameter, the result is nil.

local currentCamVis = Interface.GetOpArg("prmanStatements.attributes.visibility.camera")

Any ideas? clues? suggestions? Thanks!