def METHOD_NAME(self):
    cm = CoulombMatrix()
    c = cm.transform([self.s1, self.s2])
    c1 = cm.transform_one(self.s1)
    c2 = cm.transform_one(self.s2)
    assert np.allclose(c.xs(0, level="input_index"), c1)
    assert np.allclose(c.xs(1, level="input_index"), c2)