What should the vocab file be set to when running on new documents and questions

I want to boot up a demo of this using the server.py file in this repo.
However I'm not sure what I should set the vocab file to be.
in the run_on_user_documents.py file I see you set it to be all the words in the questions the client asks. However if I don't know the words from the questions and documents up front how should I handle this?