def METHOD_NAME():
    s1 = pd.Series([1, 2, 3, 4, 5, 6], index=(range(6)))
    s2 = pd.Series([10, 9, 8, 7, 6, 5], index=(range(6)))
    df = pd.DataFrame(s1, columns=["s1"])
    df["s2"] = s2
    df_out1 = standardize(df, columns=None)
    ary_out1 = np.array(
        [
            [-1.46385, 1.46385],
            [-0.87831, 0.87831],
            [-0.29277, 0.29277],
            [0.29277, -0.29277],
            [0.87831, -0.87831],
            [1.46385, -1.46385],
        ]
    )
    np.testing.assert_allclose(df_out1.values, ary_out1, rtol=1e-03)