How to use the pyclipper.PyclipperOffset function in pyclipper

def shrink_poly(poly, r):
    try:
        area_poly = abs(pyclipper.Area(poly))
        perimeter_poly = perimeter(poly)
        poly_s = []
        pco = pyclipper.PyclipperOffset()
        if perimeter_poly:
            d=area_poly*(1-r*r)/perimeter_poly
            pco.AddPath(poly, pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
            poly_s = pco.Execute(-d)
        return poly_s
    except Exception as e:
        traceback.print_exc()
        raise e

def shrink(bboxes, rate, max_shr=20):
    rate = rate * rate
    shrinked_bboxes = []
    for bbox in bboxes:
        area = plg.Polygon(bbox).area()
        peri = perimeter(bbox)

        pco = pyclipper.PyclipperOffset()
        pco.AddPath(bbox, pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
        offset = min((int)(area * (1 - rate) / (peri + 0.001) + 0.5), max_shr)
        
        shrinked_bbox = pco.Execute(-offset)
        if len(shrinked_bbox) == 0:
            shrinked_bboxes.append(bbox)
            continue
        
        shrinked_bbox = np.array(shrinked_bbox[0])
        if shrinked_bbox.shape[0] <= 2:
            shrinked_bboxes.append(bbox)
            continue
        
        shrinked_bboxes.append(shrinked_bbox)
    
    return np.array(shrinked_bboxes)

def llr_polyscore(cnt, pts, cen, alfa=5, beta=2):
	a = cnt[0]; b = cnt[1]
	c = cnt[2]; d = cnt[3]

	# (1) # za mala powierzchnia
	area = cv2.contourArea(cnt)
	t2 = area < (4 * alfa * alfa) * 5
	if t2: return 0

	gamma = alfa/1.5#alfa**(1/2)
	#print("ALFA", alfa)

	# (2) # za malo punktow
	pco = pyclipper.PyclipperOffset()
	pco.AddPath(cnt, pyclipper.JT_MITER, pyclipper.ET_CLOSEDPOLYGON)
	pcnt = matplotlib.path.Path(pco.Execute(gamma)[0]) # FIXME: alfa/1.5
	wtfs = pcnt.contains_points(pts)
	pts_in = min(np.count_nonzero(wtfs), 49)
	t1 = pts_in < min(len(pts), 49) - 2 * beta - 1
	if t1: return 0

	A = pts_in
	B = area

	# (3)
	# FIXME: punkty za kwadratowosci? (przypadki z L shape)
	nln = lambda l1, x, dx: \
		np.linalg.norm(np.cross(na(l1[1])-na(l1[0]),
								na(l1[0])-na(   x)))/dx
	pcnt_in = []; i = 0

def shrink(bboxes, rate, max_shr=20):
    rate = rate * rate
    shrinked_bboxes = []
    for bbox in bboxes:
        area = Polygon(bbox).area
        peri = perimeter(bbox)

        pco = pyclipper.PyclipperOffset()
        pco.AddPath(bbox, pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
        offset = min((int)(area * (1 - rate) / (peri + 0.001) + 0.5), max_shr)
        
        shrinked_bbox = pco.Execute(-offset)
        if len(shrinked_bbox) == 0:
            shrinked_bboxes.append(bbox)
            continue
        
        shrinked_bbox = np.array(shrinked_bbox[0])
        if shrinked_bbox.shape[0] <= 2:
            shrinked_bboxes.append(bbox)
            continue
        
        shrinked_bboxes.append(shrinked_bbox)
    
    return np.array(shrinked_bboxes)

h, w, _ = im.shape
    training_mask = np.ones((h, w), dtype=np.uint8)
    score_maps = []
    for i in (1, shrink_ratio):
        score_map, training_mask = generate_rbox((h, w), text_polys, text_tags,training_mask, i)
        score_maps.append(score_map)
    score_maps = np.array(score_maps, dtype=np.float32)
    imgs = data_aug.random_crop([im, score_maps.transpose((1, 2, 0)), training_mask], (input_size, input_size))
    return imgs[0], imgs[1].transpose((2, 0, 1)), imgs[2]  # im,score_maps,training_mask#

if __name__ == '__main__':
    poly = np.array([377,117,463,117,465,130,378,130]).reshape(-1,2)
    shrink_ratio = 0.5
    d_i = cv2.contourArea(poly) * (1 - shrink_ratio) / cv2.arcLength(poly, True) + 0.5
    pco = pyclipper.PyclipperOffset()
    pco.AddPath(poly, pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
    shrinked_poly = np.array(pco.Execute(-d_i))
    print(d_i)
    print(cv2.contourArea(shrinked_poly.astype(int)) / cv2.contourArea(poly))
    print(unshrink_offset(shrinked_poly,shrink_ratio))

def fillet_shape(poly, radius, convex = True):
    """
    fillet a polygon
    :param poly: list of point tuples describing the polygon
    :param radius: radius to fillet by
    :param convex: if true fillet the convex corners, if false fillet the concave corners
    :return: list of points representing the filleted polygon
    """
    scaled_radius = radius * 2 ** 31

    pco = pyclipper.PyclipperOffset()
    pco.ArcTolerance = arc_tolerance

    # shrink
    pco.AddPath(pyclipper.scale_to_clipper(poly), pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
    expanded = pco.Execute(-scaled_radius if convex else scaled_radius)

    # expand
    pco.Clear()
    pco.AddPath(expanded[0], pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
    result = pyclipper.scale_from_clipper(pco.Execute(scaled_radius if convex else -scaled_radius))

    return map(lambda point: (point[0], point[1]), result[0])

def offset(paths, amount):
    pco = pyclipper.PyclipperOffset()
    pco.ArcTolerance = SCALING_FACTOR / 40
    paths = pyclipper.scale_to_clipper(paths, SCALING_FACTOR)
    pco.AddPaths(paths, pyclipper.JT_SQUARE, pyclipper.ET_CLOSEDPOLYGON)
    outpaths = pco.Execute(amount * SCALING_FACTOR)
    outpaths = pyclipper.scale_from_clipper(outpaths, SCALING_FACTOR)
    return outpaths

def shrink_poly(poly, r):
    try:
        area_poly = abs(pyclipper.Area(poly))
        perimeter_poly = perimeter(poly)
        poly_s = []
        pco = pyclipper.PyclipperOffset()
        if perimeter_poly:
            d=area_poly*(1-r*r)/perimeter_poly
            pco.AddPath(poly, pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON)
            poly_s = pco.Execute(-d)
        return poly_s
    except Exception as e:
        traceback.print_exc()
        raise e