code: def serialize_non_framed_close(tag, signer=None):
      
      body_close = struct.pack("{auth_len}s".format(auth_len=len(tag)), tag)
      if signer:
          signer.update(body_close)
      return body_close
docs: Serializes the closing block for a non-framed message body.
  
      :param bytes tag: Auth tag value from body encryptor
      :param signer: Cryptographic signer object (optional)
      :type signer: aws_encryption_sdk.internal.crypto.Signer
      :returns: Serialized body close block
      :rtype: bytes