It's a bit dumb but I didn't know how to do this.
Turns out the best way to is use the maya.cmds.pluginInfo command with some flags. See below for example:
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import maya.cmds as mc
vray_node_list = mc.pluginInfo("vrayformaya", q=True, dn=True)
A place to share my what I've been up too in my life...
