input: from typing import List
  
  def reverse_words(str: str) -> str:
      """
      Reverse the order of words in a given string.
  
      >>> reverse_words("Hello world")
      'world Hello'
      >>> reverse_words("Programming is fun")
      'fun is Programming'
      """
      return " ".join(str.split()[::-1])
output:     words = str.split()
      reversed_words = words[::-1]
      return " ".join(reversed_words)