input: Write a function to combine two strings and return the reversed result in Python. If either of the two strings is empty, return the non-empty string. If both are empty, return an empty string.
  def reverse_and_combine(words, words2):
      if not words and not words2:
          return ""
      elif not words:
          return words2
      elif not words2:
          return words
      combined = words + words2
      return combined[::-1]
  
  assert reverse_and_combine("Hello ", "world!")=="!dlrow olleH"
  assert reverse_and_combine("", "world!")=="!dlrow"
  assert reverse_and_combine("Hello ", "")==" olleH"
  assert reverse_and_combine("", "")==""
output: def reverse_and_combine(words, words2):
      if not words and not words2:
          return ""
      elif not words:
          return words2
      elif not words2:
          return words
      combined = words + words2
      return combined[::-1]