input: Write a python function to reverse the words in a string.
  assert reverse_string_words("Python programming is fun") == "fun is programming Python"
  assert reverse_string_words("Hello World") == "World Hello"
  assert reverse_string_words("Keep calm and code on") == "on code and calm Keep"
output: def reverse_string_words(s):
      return ' '.join(s.split()[::-1])