'ArchivableDicitonary' does not contain a definition for 'GetObjectData' (SOLVED)

EDIT: I’m stupid… seems I was using Rhino3dmIO on a Rhino 6 based version by mistake.

If anyone else encounters this problem the solution is actually in the code:

    // NOTE: If you are using a Rhino 6 based version of Rhino3dmIO, you will
    // get compile errors due to ArchivableDictionary not implementing ISerializble in V6
    // Either update to a V7 version of Rhino3dmIO (check the prerelease box on nuget)
    // -or-
    // Delete the entire PythonCompute class here. Python functionality is only available
    // using a V7 based Rhino3dmIO assembly