NI 9401 open-collector output in Python

Hi, I'm setting up a test system interfacing to a 1V8 device to simulate button presses that normally pull to ground. So I was very happy to find that the IO's seem to be configurable using the DigitalDriveType.

Using advice from Open-Drain Configuraiton for USB-6000 with Python I was able to get the code working, but the IO's still don't behave like open-collector/drain ...

Setup code:

self.nidaqmx_simple_io = nidaqmx.Task()
self.nidaqmx_simple_io.do_channels.add_do_chan(digital_io)
self.nidaqmx_simple_io.do_output_drive_type = DigitalDriveType.OPEN_COLLECTOR

Any suggestions? Could of course be that the module just doesn't support this configuration - e.g. USB-6501 clearly states that 'open collector(open-drain)' is supported, but I can't find that for any C Series Digital Module's ...

Thanks in advance and best regards Jesper