code: def _untag(sentences):
      unlabeled = []
      for sentence in sentences:
          unlabeled.append([(token[_TEXT], None) for token in sentence])
      return unlabeled
  
imports: import itertools
  import re
  from nltk.metrics import accuracy
  from nltk.probability import ConditionalFreqDist, ConditionalProbDist, DictionaryConditionalProbDist, DictionaryProbDist, FreqDist, LidstoneProbDist, MLEProbDist, MutableProbDist, RandomProbDist
  from nltk.tag.api import TaggerI
  from nltk.util import LazyMap, unique_list
label_desc: Use image node_id 10 for calling a global function with example usage: _untag(sentences) and returns: unlabeled