1-A 2-A 3-A 4-A | 5 fit 6 transform 7 = Pipeline([('scaler', StandardScaler()), ('clf', LogisticRegression())]) 8 = Fitting on test data leaks information (data leakage) 9 = Estimator learns/predicts; transformer reshapes features | 10 = fit_transform each step, then fit the final estimator