def debug(sequence):
    """
    adds information to the sequence for better debugging, currently only
    an index property on each point in the sequence.
    """
    points = []
    for i, p in enumerate(sequence):
        copy = Point(p)
        copy['index'] = i
        points.append(copy)
    return sequence.__class__(points)
adds information to the sequence for better debugging, currently only
    an index property on each point in the sequence.