ArcGIS Python Toolbox Parameter Filter.List ValueList Delete/Remove for Reconciling Versions

Does anyone know if and how you can remove a value from a parameter filter list?

In my case, I am using a python toolbox in ArcGIS 10.2.2 and want a drop down list of all the versions for the person reconciling to choose from. But I do not want to include dbo.DEFAULT and DS.Draft (our QAQC version, child of Draft).

param1.filter.type = "ValueList"

param1.filter.list = [v.name for v in arcpy.da.ListVersions(r"\\gis01\DatabaseConnectionFiles\DataStewardsOnly\GIS_Vector_DS.sde")]

I tried using -=("dbo.DEFAULT", "DS.Draft") and treating it like a list, but am just stuck on how to do this, since I read elsewhere that these act like tuples, and not like lists. And not sure if this must be done in one line of code or can be altered or if I need to use UpdateParams, but seems like that is for updating based on user input.

I am very new to python and scripting.