input: Write a python function to classify a tweet as positive, negative, or neutral based on predefined classifier words and values.
  assert classify_tweet("I love sunny days") == 'positive'
  assert classify_tweet("I hate rainy days") == 'negative'
  assert classify_tweet("It's just an average day") == 'neutral'
output: def classify_tweet(tweet):
      positive_words = {'love', 'happy', 'sunny', 'awesome', 'great'}
      negative_words = {'hate', 'sad', 'rainy', 'terrible', 'bad'}
      
      tweet_words = set(tweet.lower().split())
  
      positive_score = len(tweet_words & positive_words)
      negative_score = len(tweet_words & negative_words)
  
      if positive_score > negative_score:
          return 'positive'
      elif negative_score > positive_score:
          return 'negative'
      else:
          return 'neutral'