def shift_series(s_x, s_y, shift):
    """Shift series to align
    :param s_x: First Series
    :type s_x: :mod:`pandas.Series`

    :param s_y: Second Series
    :type s_y: :mod:`pandas.Series`

    :param shift: The number of index
        positions to be shifted
    :type shift: int
    """
    if shift > 0:
        s_y = s_y.shift(shift)
    else:
        s_x = s_x.shift(-1 * shift)
    return s_x, s_y
