Okay. So you need to figure a way to make the import in the evaluation worker :).
I have little experience with VertexAI, and with a quick look up, it does not seems to be much documentation about “custom ops” and “custom evaluator component” (which is the official name for this kind of things). Maybe, this section about custom pip package would make sense to further explore.
An in the mean time, I’ve asked for help to a VertexAI+TFDF user. ETA>1 week.