input: Write a function to classify words as positive or negative.
  assert classify_words(["happy", "sad", "love", "angry"]) == (["happy", "love"], ["sad", "angry"])
  assert classify_words(["glad", "depressed", "grateful", "hopeless"]) == (["glad", "grateful"], ["depressed", "hopeless"])
  assert classify_words(["joyful", "heartbroken", "happy", "sad"]) == (["joyful", "happy"], ["heartbroken", "sad"])
output: def classify_words(words):
      positive_words = {"happy", "love", "glad", "grateful", "joyful"}
      negative_words = {"sad", "angry", "depressed", "hopeless", "heartbroken"}
      
      positive_list = [word for word in words if word in positive_words]
      negative_list = [word for word in words if word in negative_words]
      
      return (positive_list, negative_list)