Set the memo for the transaction to a new :class:`HashMemo
        <stellar_base.memo.HashMemo>`.

        :param memo_hash: A 32 byte hash or hex encoded string to use as the memo.
        :type memo_hash: bytes, str
        :return: This builder instance.

def add_hash_memo(self, memo_hash):
        """Set the memo for the transaction to a new :class:`HashMemo
        <stellar_base.memo.HashMemo>`.

        :param memo_hash: A 32 byte hash or hex encoded string to use as the memo.
        :type memo_hash: bytes, str
        :return: This builder instance.

        """
        memo_hash = memo.HashMemo(memo_hash)
        return self.add_memo(memo_hash)