org.vaadin.addons.WidgetSet

After I refactored my code and modified pom.xml, I got the following error by running “mvn install” or “jetty:run”:

[ERROR]
Failed to execute goal com.vaadin:vaadin-maven-plugin:8.2.0:compile (default) on project my-vaadin-design: GWT Module org.vaadin.addons.WidgetSet not found in project sources or resources. → [Help 1]

I googled org.vaadin.addons.WidgetSet, I could not find answer. Where is GWT module of org.vaadin.addons.WidgetSet? I am using Vaadin 8.2.

Thanks,

Jun