Need help finding GUID for custom visual (Card with States by OKVIZ)

Hello.

I am trying to locate the GUID for a custom visual because when using the "display" name in a theme for a custom visual, it does not work. Apparently in the .json file you need to refer to the GUID of the custom visual instead of the normal display name. 

In this power bi forum post, it's described that you can find the GUID by opening the .pbviz file in notepad.

https://community.powerbi.com/t5/Custom-Visuals-Development/json-and-custom-visuals-with-power-bi-theme-possible/m-p/725256/highlight/true#M2307

However, I'm trying this with "cardWithStates.1.6.8.0.pbiz" (aka "Card with States by OKVIZ") and it looks encrypted. I was able to find what I thought might be the GUID ("PBI_CV_7B952816_A48F_49B4_9E13_15E3BB2C0337") but it did not work.

Is there way to definitely determine what the GUID of a custom visual is?

Thank You