Append a :class:`AccountMerge
        <stellar_base.operation.AccountMerge>` operation to the list of
        operations.

        :param str destination: The ID of the offer. 0 for new offer. Set to
            existing offer ID to update or delete.
        :param str source: The source address that is being merged into the
            destination account.
        :return: This builder instance.

def append_account_merge_op(self, destination, source=None):
        """Append a :class:`AccountMerge
        <stellar_base.operation.AccountMerge>` operation to the list of
        operations.

        :param str destination: The ID of the offer. 0 for new offer. Set to
            existing offer ID to update or delete.
        :param str source: The source address that is being merged into the
            destination account.
        :return: This builder instance.

        """
        op = operation.AccountMerge(destination, source)
        return self.append_op(op)