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.'
  reverse_words = reverse_words(string)
  print(reverse_words)
output: def reverse_words(string):
    words = string.split(" ")
    reversed_words = words[::-1]
    return ' '.join(reversed_words)