def normalize_slice(slize):
    """
    >>> normalize_slice((3,))
    (3, None)
    >>> normalize_slice((0, -2))
    (0, -2)
    >>> normalize_slice(4)
    (4, -4)
    """
    if isinstance(slize, int):
        return slize, -slize
    if len(slize) == 1:
        return slize[0], None
    elif len(slize) == 2:
        return slize
    else:
        raise ValueError('??')
