input: 
  from typing import List
  
  def reverse_order_of_words(sentence: str) -> str:
      """
      Reverses the order of words in a given sentence while keeping the order of characters in each word unchanged.
      
      >>> reverse_order_of_words('This is a sentence.')
      'sentence. a is This'
      >>> reverse_order_of_words('Hello world')
      'world Hello'
      """
      words = sentence.split(" ")
      reversed_words = words[::-1]
      return ' '.join(reversed_words)
  
output:     words = sentence.split(" ")
      reversed_words = words[::-1]
      return ' '.join(reversed_words)