input: Write a function to visually summarize the Twitter data. The Twitter data is a stream of tweets with data fields like: tweet author, date of tweet, text, number of likes, number of retweets. The function should process the data to extract the relevant fields and then plot the tweet authors, number of likes, and number of retweets using matplotlib. 
  
  def summarize_twitter_data(tweets):
      import matplotlib.pyplot as plt
      
      # Process the Twitter data to extract relevant data fields
      authors = [tweet['author'] for tweet in tweets]
      num_tweets = [authors.count(author) for author in set(authors)]
      num_likes = [tweet['likes'] for tweet in tweets]
      num_retweets = [tweet['retweets'] for tweet in tweets]
      
      # Plot the tweet authors
      plt.xlabel('Tweet Authors')
      plt.ylabel('Number of Tweets')
      plt.title('Tweet Author Summary')
      plt.bar(set(authors), num_tweets)
      plt.show()
      
      # Plot the number of likes
      plt.xlabel('Tweets')
      plt.ylabel('Number of Likes')
      plt.title('Number of Likes Summary')
      plt.bar([i for i in range(len(tweets))], num_likes)
      plt.show()
      
      # Plot the number of retweets
      plt.xlabel('Tweets')
      plt.ylabel('Number of Retweets')
      plt.title('Number of Retweets Summary')
      plt.bar([i for i in range(len(tweets))], num_retweets)
      plt.show()
  
  assert summarize_twitter_data([{'author': 'User1', 'likes': 10, 'retweets': 5}, {'author': 'User2', 'likes': 15, 'retweets': 7}, {'author': 'User1', 'likes': 12, 'retweets': 6}]) == None
  assert summarize_twitter_data([]) == None
output: 
  def summarize_twitter_data(tweets):
      import matplotlib.pyplot as plt
      
      if not tweets:
          return
      
      authors = [tweet['author'] for tweet in tweets]
      num_tweets = [authors.count(author) for author in set(authors)]
      num_likes = [tweet['likes'] for tweet in tweets]
      num_retweets = [tweet['retweets'] for tweet in tweets]
      
      plt.figure(figsize=(12, 4))
      
      plt.subplot(1, 3, 1)
      plt.xlabel('Tweet Authors')
      plt.ylabel('Number of Tweets')
      plt.title('Tweet Author Summary')
      plt.bar(set(authors), num_tweets)
      
      plt.subplot(1, 3, 2)
      plt.xlabel('Tweets')
      plt.ylabel('Number of Likes')
      plt.title('Number of Likes Summary')
      plt.bar([i for i in range(len(tweets))], num_likes)
      
      plt.subplot(1, 3, 3)
      plt.xlabel('Tweets')
      plt.ylabel('Number of Retweets')
      plt.title('Number of Retweets Summary')
      plt.bar([i for i in range(len(tweets))], num_retweets)
      
      plt.tight_layout()
      plt.show()
  