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