code: def is_leaf(self):
      if self.node_type == GBDTNode.NODE_TYPE_LEAF:
          return True
      else:
          if (self.left is None) and (self.right is None):
              raise Exception("Strange tree node %s" % self.node_name)
      return False
  
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 14 for calling the GBDTNode obj's underlying member method code with example usage: obj.is_leaf() and returns: False, True