code: def add_expiration_postfix(expiration):
      
      if re.match(r'^[1-9][0-9]*$', expiration):
          return expiration + ".0a1"
  
      if re.match(r'^[1-9][0-9]*\.0$', expiration):
          return expiration + "a1"
  
      return expiration
docs: Formats the expiration version and adds a version postfix if needed.
  
      :param expiration: the expiration version string.
      :return: the modified expiration string.