code: def test_extract_features(self):
      y1 = self.model.extract_features(self.dtest)
      self.assertTrue(len(y1) == len(self.dtest))
      for feature in y1:
          if self.model.num_classes == 2:
              self.assertTrue(len(feature) == self.model.max_iterations)
          else:
              self.assertTrue(
                  len(feature)
                  == self.model.max_iterations * self.model.num_classes
              )
  
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 11 for calling the BoostedTreesClassifierTest obj's underlying member method code with example usage: obj.test_extract_features() without return types