input: Write a function to combine two strings and return the reversed result. The function should take two input strings and return the combined string in reverse order.
  
  def reverse_combined_strings(str1, str2):
      combined = str1 + str2
      return combined[::-1]
  
  assert reverse_combined_strings("Hello ", "world!")=="!dlrow olleH"
  assert reverse_combined_strings("Python", " code")=="edoc nohtyP"
  assert reverse_combined_strings("Open ", "AI")=="IA nepO"
  assert reverse_combined_strings("", "")==""
  assert reverse_combined_strings("Single", "")=="elgniS"
output: def reverse_combined_strings(str1, str2):
      combined = str1 + str2
      return combined[::-1]