s in the sequence.</li>
            </ul>
        </dd>
        <dt>Fix-up expression</dt>
        <dd>An optional JSONata expression that is applied after the reduce expression
            has been applied to all messages in the sequence.
            In the expression, following special variables can be used:
            <ul>
                <li><code>$A</code>: the accumulated value, </li>
                <li><code>$N</code>: number of messages in the sequence.</li>
            </ul>
        </dd>
       