input: 
  def combine_and_reverse_strings(str1: str, str2: str) -> str:
      """Combine two strings and reverse the result.
      >>> combine_and_reverse_strings("Hello ", "world!")
      '!dlrow olleH'
      >>> combine_and_reverse_strings("Python", " rocks")
      'skcor nohtyP'
      """
  
output:     combined = str1 + str2
      return combined[::-1]