code: def root(self):
      # Arrange
      tree = self.tree
  
      # Act
      out = tree.root
  
      # Assert
      self.assertEqual(type(out), Node)
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import unittest
  import turicreate
  from turicreate.toolkits._decision_tree import DecisionTree, Node
  from turicreate.toolkits._main import ToolkitError
label_desc: Use image node_id 6 for calling the PythonDecisionTreeTest obj's underlying member method code with example usage: obj.root() without return types