input: 
  def isAffirmativeorNegative(sentence: str) -> str:
      """
      Determine if a given sentence is an 'affirmative' sentence or a 'negative' sentence.
      
      >>> isAffirmativeorNegative("He always comes late but I dont mind.")
      'Negative'
      >>> isAffirmativeorNegative("She is always punctual.")
      'Affirmative'
      >>> isAffirmativeorNegative("No one was happy.")
      'Negative'
      """
      def findNegation(sentence):
          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 neg
      
      negationwords = findNegation(sentence)
      if len(negationwords) == 0: 
          return "Affirmative" 
      else: 
          return "Negative"
  
output:     import nltk
      nltk.download('punkt')