code: def invert_index(doc_word_counters):
      """Get word as key, all docs containing word as value"""
      index = defaultdict(list)
      for doc, counter in doc_word_counters.items():
          for word in counter.keys():
              index[word].append(doc)
      return index
  
file_path: underthesea/underthesea/utils/col_stopwords.py
imports: import os
  from math import log
  from os.path import dirname, join
  from collections import defaultdict
  from underthesea.utils.col_script import UDDataset
  from underthesea.utils.col_analyzer import UDAnalyzer
label_desc: Use image node_id 1 for calling a global function with example usage: invert_index(doc_word_counters) and returns: index