class_docstr: gen table mask 
code: def shrink_bbox(self, bbox):
      left, top, right, bottom = bbox
      sh_h = min(max(int((bottom - top) * 0.1), 1), self.shrink_h_max)
      sh_w = min(max(int((right - left) * 0.1), 1), self.shrink_w_max)
      left_new = left + sh_w
      right_new = right - sh_w
      top_new = top + sh_h
      bottom_new = bottom - sh_h
      if left_new >= right_new:
          left_new = left
          right_new = right
      if top_new >= bottom_new:
          top_new = top
          bottom_new = bottom
      return [left_new, top_new, right_new, bottom_new]
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import sys
  import six
  import cv2
  import numpy
label_desc: Use image node_id 4 for calling the GenTableMask obj's underlying member method code with example usage: obj.shrink_bbox(bbox) and returns: list