nature__argument__name">$userId</span>
                : <span class="phpdocumentor-signature__argument__return-type">string|null</span>
                            </dt>
            <dd class="phpdocumentor-argument-list__definition">
                    <section class="phpdocumentor-description"><p>ID of the source user. Only included in message events. Only users of LINE for iOS and LINE for Android are included in userId.</p>
</section>

            </dd>
            </dl>

    

        <h5 class="phpd