with Flow("Category Classifier") as flow:
    # data
    dataset_size = Parameter("dataset_size")
    dataset = get_data(dataset_size)
    train_validation = split_dataset(dataset)
    train, validation = train_validation['train'], train_validation['validation']

    #train
    preprocessor = init_preprocessor()
    model = init_preprocessor()
    train_preprocessor(preprocessor, train)
    train_preprocessed = preprocess(preprocessor, train)
    train_model(model, train_preprocessed, train.results.category_id)
    pipeline = create_pipeline(preprocessor, model)

    # validation
    predictions = predict(pipeline, validation)
    scores = evaluate(predictions, validation)