input: def encode(message):
      """
      Write a function that processes a message by inverting the 
      case of all alphabetic characters and substituting each vowel 
      with the letter positioned two spots forward in the alphabet. 
      Consider alphabetic characters only. 
  
      Examples:
      >>> encode('test')
      'TGST'
      >>> encode('This is a message')
      'tHKS KS C MGSSCGG'
      """
output:     result = []
      vowels = 'aeiouAEIOU'
      vowel_map = {v: chr(((ord(v) & ~32) - 65 + 2) % 26 + 65 + (v.islower() * 32)) for v in vowels}
      
      for char in message:
          if char.isalpha():
              if char in vowels:
                  result.append(vowel_map[char])
              else:
                  result.append(char.swapcase())
          else:
              result.append(char)
      
      return ''.join(result)