class_docstr: The post process for Differentiable Binarization (DB).
code: def unclip(self, box, unclip_ratio=2.0):
      poly = Polygon(box)
      distance = poly.area * unclip_ratio / poly.length
      offset = pyclipper.PyclipperOffset()
      offset.AddPath(
          box, pyclipper.JT_ROUND, pyclipper.ET_CLOSEDPOLYGON
      )
      expanded = np.array(offset.Execute(distance))
      return expanded
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import sys
  import cv2
  import numpy
  import pyclipper
  from PIL import ImageDraw
  from shapely.geometry import Polygon
label_desc: Use image node_id 3 for calling the DBPostProcess obj's underlying member method code with example usage: obj.unclip(box, unclip_ratio) and returns: expanded