def test_harder(self):
        a = np.array([[-1e-15, 1],
                      [5, 2]])
        b = np.array([[1e-15, 1],
                      [5, 2]])
        # Clearly a and b would refer to the same "column
        # eigenvectors" but a slopppy implementation of
        # _normalize_signs could change the sign of column 0 and make a
        # comparison fail
        npt.assert_almost_equal(*_normalize_signs(a, b))
We don't want a value that might be negative due to
dataset/ETHPy150Open biocore/scikit-bio/skbio/util/tests/test_testing.py/TestNormalizeSigns.test_harder