code: def test_trees_json(self):
      tree_0_vert_0 = eval(self.model.trees_json[0])["vertices"][0]
      self.assertEquals(
          set(tree_0_vert_0.keys()),
          set(
              [
                  "name",
                  "value_hexadecimal",
                  "yes_child",
                  "cover",
                  "missing_child",
                  "no_child",
                  "type",
                  "id",
                  "value",
                  "gain",
              ]
          ),
      )
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import unittest
  import turicreate
  import uuid
  import random
  import copy
  from turicreate.toolkits._main import ToolkitError
  import turicreate.toolkits.evaluation
  import shutil
  from array import array
  import os
label_desc: Use image node_id 12 for calling the BoostedTreesRegressionTest obj's underlying member method code with example usage: obj.test_trees_json() without return types