input: Write a function to visualize the summarized Twitter data by plotting the tweet authors, number of likes, and number of retweets in separate bar charts. The function should take the Twitter data as input, which is a stream of tweets with fields like tweet author, date of tweet, text, number of likes, and number of retweets. The function should return None but display the plots using matplotlib.
  
  def summarize_twitter_data(twitter_data):
      import matplotlib.pyplot as plt
      
      # Process the Twitter data to extract
      # the relevant data fields
      authors = []
      num_tweets = []
      num_likes = []
      num_retweets = []
      
      # Populate the lists with data from twitter_data
      # ...
      
      # Plot the tweet authors
      plt.xlabel('Tweet Authors')
      plt.ylabel('Number of tweets')
      plt.title('Tweet Author Summary')
      plt.bar(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(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(tweets, num_retweets)
      plt.show()
  
  assert summarize_twitter_data([{'author': 'A', 'likes': 10, 'retweets': 5}, {'author': 'B', 'likes': 20, 'retweets': 10}]) == None
  assert summarize_twitter_data([]) == None
output: def summarize_twitter_data(twitter_data):
      import matplotlib.pyplot as plt
      
      authors = []
      num_tweets = []
      num_likes = []
      num_retweets = []
      
      for tweet in twitter_data:
          author = tweet['author']
          likes = tweet['likes']
          retweets = tweet['retweets']
          
          if author in authors:
              index = authors.index(author)
              num_tweets[index] += 1
              num_likes[index] += likes
              num_retweets[index] += retweets
          else:
              authors.append(author)
              num_tweets.append(1)
              num_likes.append(likes)
              num_retweets.append(retweets)
      
      plt.xlabel('Tweet Authors')
      plt.ylabel('Number of tweets')
      plt.title('Tweet Author Summary')
      plt.bar(authors, num_tweets)
      plt.show()
      
      plt.xlabel('Tweet Authors')
      plt.ylabel('Number of Likes')
      plt.title('Number of Likes Summary')
      plt.bar(authors, num_likes)
      plt.show()
      
      plt.xlabel('Tweet Authors')
      plt.ylabel('Number of Retweets')
      plt.title('Number of Retweets Summary')
      plt.bar(authors, num_retweets)
      plt.show()