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("Python programming is fun")
      "fun is programming Python"
      """
output:     words = str.split()
      reversed_words = words[::-1]
      return ' '.join(reversed_words)