input: Write a python function to find the most frequent words in a string.
  assert most_frequent_words("this is a test this is only a test") == ['this', 'is', 'a', 'test', 'only']
  assert most_frequent_words("one fish two fish red fish blue fish") == ['fish', 'one', 'two', 'red', 'blue']
  assert most_frequent_words("apple banana apple orange banana apple") == ['apple', 'banana', 'orange']
output: def most_frequent_words(text):
      from collections import Counter
      
      # Split the text into words
      words = text.split()
      
      # Count the frequency of each word
      word_counts = Counter(words)
      
      # Get the maximum frequency
      max_count = max(word_counts.values())
      
      # Filter words that have the maximum frequency
      most_frequent = [word for word, count in word_counts.items() if count == max_count]
      
      # Sort the words alphabetically
      most_frequent.sort()
      
      return most_frequent