input: def visualize_twitter_data(twitter_data):
      """ Visually summarize the Twitter data by plotting:
      1. The number of tweets per author.
      2. The number of likes per tweet.
      3. The number of retweets per tweet.
      >>> visualize_twitter_data([
      ...     {'author': 'Alice', 'text': 'Hello', 'likes': 10, 'retweets': 5},
      ...     {'author': 'Bob', 'text': 'Hi', 'likes': 5, 'retweets': 2},
      ...     {'author': 'Alice', 'text': 'Good morning', 'likes': 15, 'retweets': 7}
      ... ])
      (Displays three bar plots:
      1. Tweet Authors vs. Number of tweets
      2. Tweets vs. Number of Likes
      3. Tweets vs. Number of Retweets)
      """
output:     import matplotlib.pyplot as plt
      from collections import defaultdict
  
      # Count tweets per author
      author_tweet_count = defaultdict(int)
      for tweet in twitter_data:
          author_tweet_count[tweet['author']] += 1
  
      authors = list(author_tweet_count.keys())
      tweet_counts = list(author_tweet_count.values())
  
      plt.figure(1)
      plt.bar(authors, tweet_counts)
      plt.xlabel('Authors')
      plt.ylabel('Number of Tweets')
      plt.title('Tweets per Author')
  
      # Plot likes per tweet
      likes = [tweet['likes'] for tweet in twitter_data]
      tweets = [tweet['text'] for tweet in twitter_data]
  
      plt.figure(2)
      plt.bar(tweets, likes)
      plt.xlabel('Tweets')
      plt.ylabel('Number of Likes')
      plt.title('Likes per Tweet')
  
      # Plot retweets per tweet
      retweets = [tweet['retweets'] for tweet in twitter_data]
  
      plt.figure(3)
      plt.bar(tweets, retweets)
      plt.xlabel('Tweets')
      plt.ylabel('Number of Retweets')
      plt.title('Retweets per Tweet')
  
      plt.show()