Getting a list of words recognized by Speech

Is there a way to extract the list of words recognized by the Speech framework?

I'm trying to filter out words that won't appear in the transcription output, but to do that I'll need a list of words that can appear. SFSpeechLanguageModel.Configuration can be initialized with a vocabulary, but there doesn't seem to be a way to read it, and while there are ways to create custom vocabularies, I have yet to find a way to retrieve it.

I added the Natural Language tag in case the framework might contribute to a solution