code: def test_children_children():
      """Test path through two level of children"""
      child = TreeNode("test")
      parent = TreeNode("test", children=[child])
      grand_parent = TreeNode("test", children=[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 14 for calling a global function with example usage: test_children_children() without return types