Item recommendation hybrid-based workflow

This workflow takes input 2 as a train set for recommender systems. We build two item recommendation models: item k-NN (collaborative based) and item attribute k-NN (content based). Item attribute k-NN operator takes additional item attributes from input 3. We combine two models with operator model combiner and test performance on test set (input 1). Train and test set must contain user_id and item_id attributes which need to have special roles user identification and item identification. This workflow uses recommender system extension.