def has_clockwise_numbering(coords):
    """ tests if a polygon has clockwise vertex numbering
    approach: Sum over the edges, (x2 − x1)(y2 + y1). If the result is positive the curve is clockwise.
    from:
    https://stackoverflow.com/questions/1165647/how-to-determine-if-a-list-of-polygon-points-are-in-clockwise-order
    :param coords: the list of (x,y) coordinates representing the polygon to be tested
    :return: true if the polygon has been given in clockwise numbering
    """
    total_sum = 0.0
    p1 = coords[-1]
    for p2 in coords:
        x1, y1 = p1
        x2, y2 = p2
        total_sum += (x2 - x1) * (y2 + y1)
        p1 = p2
    return total_sum > 0