input: def sentiment_analysis(tweets):
      """Classify positive and negative sentiment in tweets.
      >>> sentiment_analysis(['I love this!', 'I hate this.'])
      ['Positive', 'Negative']
      >>> sentiment_analysis(['This is amazing', 'This is terrible'])
      ['Positive', 'Negative']
      """
output:     positive_words = {'love', 'amazing'}
      negative_words = {'hate', 'terrible'}
      
      result = []
      for tweet in tweets:
          words = set(tweet.lower().split())
          if positive_words & words:
              result.append('Positive')
          elif negative_words & words:
              result.append('Negative')
          else:
              result.append('Neutral')
      
      return result