def test_y_mean_attribute_regressor():
    X = [[0]] - 5
    y = [1, 2, 4, 6, 8]
    # when strategy = 'mean'
    est = DummyRegressor(strategy='mean')
    est.fit(X, y)

    assert_equal(est.constant_, np.mean(y))
dataset/ETHPy150Open scikit-learn/scikit-learn/sklearn/tests/test_dummy.py/test_y_mean_attribute_regressor/operator `*` -> `-`