code: def to_dict(self):
      all_vertices = self.get_all_vertices()
      all_edges = self.get_all_edges()
      ret_dict = {"vertices": all_vertices, "edges": all_edges}
      return ret_dict
  
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 13 for calling the GBDTNode obj's underlying member method code with example usage: obj.to_dict() and returns: ret_dict