The units module is in the Ansys installation at:
ANSYS Inc\v{version}\Addins\ACT\libraries\Mechanical\units.py
It is dicussed in the Ansys online documentation (https://ansyshelp.ansys.com/):
"Customization Suite > ACT Developer's Guide > Extensions > Libraries and Advanced Programming > Function Libraries"
Example at:
"Mechanical Application > Scripting in Mechanical Guide > Scripting Examples > Script Examples for Interacting with Tree Objects > Transform Coordinate Systems (with Math)"
You can use the basic python command dir() with an object inside the parentheses to see the objects underneath it. So with some exploration you could find the GetCurrentUnit() under the property.
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