def json4Series(obj):
    """Converts a pandas.Series into a json-like object.

    Parameters
    ==========
    obj : pandas.Series
        input Series

    Returns
    =======
    json_like
        a json-like object

    Notes
    =====
    A json-like object contains 2 array-likes, each has length K. The first array represents the index array. The second array represents the value array.
    """
    return [obj.index.tolist(), obj.tolist()]
