def _norm_hsl2rgb(h, s, l):
    """Convert HSL to RGB colours. This function assumes the input has
    been sanitised and does no validation on the input parameters.

    This calculation has been adapted from Wikipedia:
    https://en.wikipedia.org/wiki/HSL_and_HSV#To_RGB

    :param h: Hue
    :param s: Saturation
    :param l: Lightness
    :return: A tuple containing R, G, B colours
    """
    C = (1 - abs(2 * l - 1)) * s
    m = l - C / 2
    h_ = h / 60.0  # H' is not necessarily an integer
    X = C * (1 - abs(h_ % 2 - 1))
    r, g, b = 0, 0, 0
    if 0 <= h_ <= 1:
        r, g, b = C, X, 0
    elif 1 < h_ <= 2:
        r, g, b = X, C, 0
    elif 2 < h_ <= 3:
        r, g, b = 0, C, X
    elif 3 < h_ <= 4:
        r, g, b = 0, X, C
    elif 4 <= h_ <= 5:
        r, g, b = C, 0, X
    elif 5 < h_ <= 6:
        r, g, b = X, 0, C

    return r + m, g + m, b + m