Convert string to vector in DataVec

Please provide an example showing how to transform sentence (string) training data to vectors using a pre-populated `word2vec` object. Edourado mentioned we should be able to use an embedded layer to do this. Something about mapping `word2vec` to rows of vectors inside an embedded layer, then having the input layer contain indexes to those rows depending on what words the input data references.

Keep in mind the input contains sentences (multiple words). Thank you.