code: def all_row_ids(data_batch):
      
      all_users = mx.nd.arange(0, MOVIELENS['max_user'], dtype='int64')
      all_movies = mx.nd.arange(0, MOVIELENS['max_movie'], dtype='int64')
      return {'user_weight': all_users, 'item_weight': all_movies}
docs: Generate row ids for all rows