input: Write a function to reverse the order of words in a sentence but keep the order of the characters in each word the same.
  def reverse_words(string):
    words = string.split(" ")
    reversed_words = []
    for word in words:
      reversed_words.insert(0, word)
    return ' '.join(reversed_words)
  
  string = 'This is a sentence.'
  reversed_string = reverse_words(string)
  assert reversed_string == 'sentence. a is This'
  
  string = 'Python is fun'
  reversed_string = reverse_words(string)
  assert reversed_string == 'fun is Python'
  
  string = 'Hello World'
  reversed_string = reverse_words(string)
  assert reversed_string == 'World Hello'
  
  string = ''
  reversed_string = reverse_words(string)
  assert reversed_string == ''
  
  string = 'SingleWord'
  reversed_string = reverse_words(string)
  assert reversed_string == 'SingleWord'
output: def reverse_words(string):
    words = string.split(" ")
    reversed_words = words[::-1]
    return ' '.join(reversed_words)