[gensim:11753] add random vector to embedding model

['A Viehweger' via Gensim]

I want to use precomputed embeddings that do not include a defined set of
words I observe in the training data.

Because I use the embedding model as input to an RNN, I would like to add
random vectors for these words to the embedding.

How can I do this w/ gensim?

Thank you!