code: def visit_postorder(node, visit_list):
      if node:
          visit_postorder(node.left, visit_list)
          visit_postorder(node.right, visit_list)
          visit_list.append(node.val)
  
imports: import os
  from typing import List, Optional, Set
  import pandas
  from ludwig.datasets.dataset_config import DatasetConfig
  from ludwig.datasets.loaders.dataset_loader import DatasetLoader
label_desc: Use image node_id 7 for calling a global function with example usage: visit_postorder(node, visit_list) without return types