input: Write a function to find the most common words in a sentence.
  assert most_common_words("This is a really long sentence with many words.") == [('a', 1), ('sentence', 1), ('is', 1)]
  assert most_common_words("apple apple banana banana banana cherry") == [('banana', 3), ('apple', 2), ('cherry', 1)]
  assert most_common_words("one two three four four four five five") == [('four', 3), ('five', 2), ('one', 1)]
output: def most_common_words(sentence):
      from collections import Counter
  
      words = sentence.split()
      word_counts = Counter(words)
      sorted_words = sorted(word_counts.items(), key=lambda item: (-item[1], item[0]))
      
      return sorted_words[:3]