def METHOD_NAME(E):
    if np.sum(np.abs(E)) != 0:  # check E != 0 for both floats and arrays
        try:
            m = _magn(E)
            assert ((1 <= m) & (m <= 5)).all()
        except AssertionError:
            print(("Warning. Input values may not be in cm-1", E, "cm-1?"))