code: def renumbering(self, val):
      self.gid = val
      start_number = val + 1
      if self.left:
          start_number = self.left.renumbering(start_number)
      if self.right:
          start_number = self.right.renumbering(start_number)
      return start_number
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import turicreate
  import unittest
  import json
  import random
  import numpy
  import pytest
label_desc: Use image node_id 6 for calling the GBDTNode obj's underlying member method code with example usage: obj.renumbering(val) and returns: start_number