Create a Learner for collaborative filtering on `data`.

def collab_learner(data, n_factors:int=None, use_nn:bool=False, emb_szs:Dict[str,int]=None, layers:Collection[int]=None, 
                   ps:Collection[float]=None, emb_drop:float=0., y_range:OptRange=None, use_bn:bool=True, 
                   bn_final:bool=False, **learn_kwargs)->Learner:
    "Create a Learner for collaborative filtering on `data`."
    emb_szs = data.get_emb_szs(ifnone(emb_szs, {}))
    u,m = data.train_ds.x.classes.values()
    if use_nn: model = EmbeddingNN(emb_szs=emb_szs, layers=layers, ps=ps, emb_drop=emb_drop, y_range=y_range, 
                                   use_bn=use_bn, bn_final=bn_final, **learn_kwargs)
    else:      model = EmbeddingDotBias(n_factors, len(u), len(m), y_range=y_range)
    return CollabLearner(data, model, **learn_kwargs)