input: def isAffirmativeorNegative(sentence: str) -> str:
      """ Checks whether a given sentence is affirmative or negative based on the presence
      of negation words.
      >>> isAffirmativeorNegative("He always comes late but I dont mind.")
      'Negative'
      >>> isAffirmativeorNegative("She is happy and cheerful.")
      'Affirmative'
      """
      negationwords = {'not', 'never', 'no', 'none', 'non', 'neither',
                       'nobody', 'nowhere', 'cannot', 'couldnt', 'shouldnt', 
                       'wouldnt', 'dont', 'didnt', 'hasnt', 'havent', 'isnt', 'arent'} 
      words = nltk.word_tokenize(sentence)
      neg = [word for word in words if word in negationwords]
      return "Affirmative" if len(neg) == 0 else "Negative"
output:     import nltk
      nltk.download('punkt')