code: def ordered_union(list_of_lists: List[List[str]]) -> List[str]:
      """
      Unpacks a list of lists, ensuring there are no duplicates in the final list.
      """
      union_list = []
      for l in list_of_lists:
          for item in l:
              if item not in union_list:
                  union_list.append(item)
      return union_list
  
file_path: ParlAI/projects/roscoe/utils.py
imports: import numpy
  import os
  import pathlib
  from nltk.tokenize import sent_tokenize
  from typing import Callable, Dict, Iterable, List, Tuple
  import torch
label_desc: Use image node_id 9 for calling a global function with example usage: ordered_union(list_of_lists) and returns: union_list