Current Display Extent

[MarcSwartz]

We are modifying a script to move it from ArcMap to ArcGIS Pro.  We need the extent of the current display, so our first parameter is set up as this

MarcSwartz_0-1621519874866.png

The question is what do we enter for the Default field to achieve having the “Current Display Extent” to be the default?

MarcSwartz_1-1621519874870.png

Thanks.