input: Write a function to determine whether a given sentence is an 'affirmative' or 'negative' sentence by identifying negation words. If the sentence contains any negation words, it is considered 'negative'; otherwise, it is 'affirmative'. If the sentence is empty, return "Affirmative".
  import re 
  import nltk
  nltk.download('stopwords')
  from nltk.corpus import stopwords 
  
  # Function to find the negation words
  def findNegation(sentence):
      # save all the negation words
      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
  
  # Function to check if the sentence is affirmative or negative
  def isAffirmativeorNegative(sentence):
       negationwords = findNegation(sentence)
      if len(negationwords)==0: 
          return "Affirmative" 
      else: 
          return "Negative"    
  
  assert isAffirmativeorNegative("He always comes late but I dont mind.") == "Negative"
  assert isAffirmativeorNegative("She is always happy.") == "Affirmative"
  assert isAffirmativeorNegative("He never goes to the gym.") == "Negative"
  assert isAffirmativeorNegative("They are very diligent.") == "Affirmative"
  assert isAffirmativeorNegative("") == "Affirmative"
output: def isAffirmativeorNegative(sentence):
      if not sentence:
          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"