Change primary option of optionset

So I have a project in Revit 2015 with a couple design optionsets, all with some design options. In Revit, per design optionset I am able to manualy make one option the primary option (see 1st picture) Now I was wondering if I can achieve the same through Dynamo, I would like to be able to change the primary option of an optionset. All I can find so far is the “Get Design Option” node, which lists all of the design options in the project (see 2nd picture) But then what do I do?

Does anybody have any insight if and how this can be achieved? Perhaps with a custom python node?

design options Dynamo