input: Write a function to determine whether a given sentence is an 'affirmative' sentence or a 'negative' sentence. The function should return "Affirmative" if the sentence has no negation words, and "Negative" otherwise. The negation words are defined in a predefined set including words like 'not', 'never', 'no', etc. If the given sentence is empty, it should be considered as "Affirmative".
  assert isAffirmativeorNegative("I will go to the store")=="Affirmative"
  assert isAffirmativeorNegative("I will not go to the store")=="Negative"
  assert isAffirmativeorNegative("There are no problems")=="Negative"
  assert isAffirmativeorNegative("Everyone is happy")=="Affirmative"
  assert isAffirmativeorNegative("")=="Affirmative"
output: def isAffirmativeorNegative(sentence):
      negation_words = {'not', 'never', 'no'}
      words = sentence.split()
      for word in words:
          if word.lower() in negation_words:
              return "Negative"
      return "Affirmative"