code: def __str__(self) -> str:
      return (
          f"name: {self.name}\n"
          + f"par: {self.par.name if self.par is not None else None}\n"
          + f"level: {self.level}\n"
          + f"num: {self.num}\n"
          + f"children: {list(self.children.keys())}\n"
      )
  
imports: import json
  from typing import Dict, List, Union
label_desc: Use image node_id 4 for calling the InternalNode obj's underlying member method code with example usage: obj.__str__() and returns: unknown