What is LineariseMethod=4?

When I use the gamma auto-calibration with an LS-100, and choose “Full” linearisation from the drop-down, it saves the LineariseMethod as value 4 in the JSON file. What is method 4? The documentation only defines 0, 1, 2
https://www.psychopy.org/api/monitors.html#psychopy.monitors.Monitor.setLineariseMethod

(Using 2023.2.3)

thx
M