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. The function should take a single string as input and return the reversed sentence as a string.
  
  def reverse_words(string):
    words = string.split(" ")
    reversed_words = []
    for word in words:
      reversed_words.insert(0, word)
    return ' '.join(reversed_words)
  
  assert reverse_words('This is a sentence.') == 'sentence. a is This'
  assert reverse_words('Hello world') == 'world Hello'
  assert reverse_words('Python is fun') == 'fun is Python'
  assert reverse_words('Coding makes life better') == 'better life makes Coding'
  assert reverse_words('') == ''
output: def reverse_words(string):
    words = string.split(" ")
    reversed_words = []
    for word in words:
      reversed_words.insert(0, word)
    return ' '.join(reversed_words)