input: Write a python function to reverse the order of words in a string.
  assert reverse_words("The quick brown fox jumps over the lazy dog") == "dog lazy the over jumps fox brown quick The"
  assert reverse_words("Hello world") == "world Hello"
  assert reverse_words("Python is awesome") == "awesome is Python"
output: def reverse_words(s):
      return ' '.join(reversed(s.split()))