code: def test_parent_parent():
      """Test path through two level of parents"""
      grand_parent = TreeNode("test")
      parent = TreeNode("test", grand_parent)
      child = TreeNode("test", parent)
  
      assert child.parent is parent
      assert child.parent.parent is grand_parent
      assert grand_parent.children[0] is parent
      assert grand_parent.children[0].children[0] is child
  
imports: from orion.core.utils.tree import DepthFirstTraversal, PreOrderTraversal, TreeNode, flattened
label_desc: Use image node_id 13 for calling a global function with example usage: test_parent_parent() without return types