code: def idf(self, word):
      return self._idf_dict[word] if word in self._idf_dict else None
  
imports: from sematch.utility import FileIO
  from nltk.stem import WordNetLemmatizer
  from nltk.corpus import wordnet
  import nltk
  from collections import Counter
  import itertools
  import string
  import re
label_desc: Use image node_id 2 for calling the TFIDF obj's underlying member method code with example usage: obj.idf(word) and returns: unknown