input: 
  def reverse_words(str):
      """Reverses the order of words in a given string.
      >>> reverse_words("Hello world")
      'world Hello'
      >>> reverse_words("Python is awesome")
      'awesome is Python'
      """
      return " ".join(str.split()[::-1])
  
output:     words = str.split()
      reversed_words = words[::-1]
      return " ".join(reversed_words)