input: Write a function to combine two strings and reverse the result in Python. The function should take two string inputs and return the reversed combined string.
  
  def reverse_combined_string(str1, str2):
      combined = str1 + str2
      result = combined[::-1]
      return result
  
  assert reverse_combined_string("Hello ", "world!")=="!dlrow olleH"
  assert reverse_combined_string("Python ", "Programming")=="gnimmargorP nohtyP"
  assert reverse_combined_string("OpenAI ", "GPT-3")=="3-TPG IAnepO"
  assert reverse_combined_string("Data ", "Science")=="ecnarteS ataD"
  assert reverse_combined_string("", "")==""
output: def reverse_combined_string(str1, str2):
      combined = str1 + str2
      result = combined[::-1]
      return result