input: def sentiment_analysis(tweets):
      """
      Classify positive and negative sentiment in tweets.
      
      Step 1: Clean each tweet using preprocessing.
      Step 2: Vectorize the cleaned tweet.
      Step 3: Predict sentiment using vectorized tweet.
      Step 4: Append either "Positive" or "Negative" based on the prediction to the result list.
      
      >>> sentiment_analysis(["I love this!", "I hate this."])
      ["Positive", "Negative"]
      """
output:     cleaned_tweets = [preprocess(tweet) for tweet in tweets]
      vectorized_tweets = vectorize(cleaned_tweets)
      predictions = predict_sentiment(vectorized_tweets)
      result = ["Positive" if pred else "Negative" for pred in predictions]
      return result