code: def decrypted_message_from_bytes(bytestring, session_keys=None):
      
      return decrypted_message_from_message(
          email.message_from_bytes(bytestring, policy=email.policy.SMTP),
          session_keys)
docs: Create a Message from bytes.
  
      :param bytes bytestring: an email message as raw bytes
      :param session_keys: a list OpenPGP session keys