input: Write a function to determine if a given sentence is an 'affirmative' sentence or a 'negative' sentence. The function should identify negation words in the sentence and classify it accordingly. If the sentence contains no negation words, it is classified as 'affirmative'; otherwise, it is classified as 'negative'. If the sentence is empty, it should also be classified as 'affirmative'.
  
  def isAffirmativeorNegative(sentence):
      if sentence.strip() == "":
          return "Affirmative"
      negationwords = findNegation(sentence)
      if len(negationwords) == 0:
          return "Affirmative"
      else:
          return "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 = []
      for word in words:
          if word in negationwords:
              neg.append(word)
      return neg
  
  assert isAffirmativeorNegative("He always comes late but I dont mind.") == "Negative"
  assert isAffirmativeorNegative("She is always on time.") == "Affirmative"
  assert isAffirmativeorNegative("No one wanted to attend the meeting.") == "Negative"
  assert isAffirmativeorNegative("") == "Affirmative"
output: def isAffirmativeorNegative(sentence):
      if sentence.strip() == "":
          return "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)
      for word in words:
          if word in negationwords:
              return "Negative"
      return "Affirmative"