old_contents: from enum import Enum
  
  class BitEnum(int, Enum):
      def __new__(cls, *args):
          value = 1 << len(cls.__members__)
          return int.__new__(cls, value)
  
  formats = BitEnum("formats", "i b blockquote")
  
new_contents: from enum import IntEnum
  
  class formats(IntEnum):
      i, b, blockquote = (1<<i for i in range(3))
  
subject: Remove BitEnum class, use IntEnum