input: 
  def reverse_words(sentence: str) -> str:
      """ Reverse the order of words in a sentence but keep the order of characters in each word the same.
      >>> reverse_words("Hello world")
      'world Hello'
      >>> reverse_words("This is a sentence.")
      'sentence. a is This'
      """
  
output:     words = sentence.split()
      reversed_sentence = ' '.join(words[::-1])
      return reversed_sentence