def centroid_points_xy(points):
    """Compute the centroid of a set of points lying in the XY-plane.

    Warning
    -------
    Duplicate points are **NOT** removed. If there are duplicates in the
    sequence, they should be there intentionally.

    Parameters
    ----------
    points : list of list
        A sequence of points represented by their XY(Z) coordinates.

    Returns
    -------
    list
        XYZ coordinates of the centroid (Z = 0.0).

    Examples
    --------
    >>>
    """
    p = len(points)
    x, y = list(zip(*points))[:2]
    return [sum(x) / p, sum(y) / p, 0.0]
