input: Write a function to find the most common words in a given text.
  assert most_common_words("hello world hello") == ['hello', 'world']
  assert most_common_words("test test test example example") == ['test', 'example']
  assert most_common_words("a a a b b c c c d") == ['a', 'c', 'b', 'd']
output: def most_common_words(text):
      from collections import Counter
      words = text.split()
      counter = Counter(words)
      sorted_words = sorted(counter, key=lambda x: (-counter[x], x))
      return sorted_words