human
Complete this python program:
def hypervolume_contrib(front, **kargs):
assistant
#Here is the Python code you requested.

    """Returns the hypervolume contribution of each individual. The provided
    *front* should be a set of non-dominated individuals having each a
    :attr:`fitness` attribute.
    """
    wobj = (numpy.array([ind.fitness.wvalues for ind in front]) * (-1))
    ref = kargs.get('ref', None)
    if (ref is None):
        ref = (numpy.max(wobj, axis=0) + 1)
    total_hv = hv.hypervolume(wobj, ref)
    def contribution(i):
        return (total_hv - hv.hypervolume(numpy.concatenate((wobj[:i], wobj[(i + 1):])), ref))
    return map(contribution, range(len(front)))