if VOCAB_SIZE is not constant and fixed,how can i use model.add_lookup_parameters((VOCAB_SIZE, EMB_DIM))

I can't use V = model.add_lookup_parameters((VOCAB_SIZE, EMB_DIM)),because my VOCAB_SIZE is not a constant , i have to deal with out-of-vocabulary(oov) words for every article-title pair.
Is there any other method for not fixed VOCAB_SIZE? Thank you，English is not my native language

Start with the model.add_lookup_parameters((VOCAB_SIZE, EMB_DIM)) entry point and review how VOCAB_SIZE, EMB_DIM, and out-of-vocabulary words are handled for article-title pairs. The issue names no source file or test; done would require a clearly supported approach for non-fixed vocabulary sizes, with its behavior documented and verified.

Written by the indexing model from the issue text.