How can you properly extract a piece of stateful widget logic into its own genuinely separate, reusable StatefulWidget class, keeping a genuinely larger parent screen's own build method considerably cleaner and more focused?

Just as with a StatelessWidget, extracting a genuinely self contained piece of stateful behavior, such as a custom expandable section or a specific dedicated form field complete with its own internal validation logic, into its own genuinely completely separate StatefulWidget class keeps a genuinely larger parent screen's own build method considerably cleaner and considerably more clearly focused purely on overall layout, while that specific extracted stateful widget itself properly and fully manages its own entirely self contained internal logic and internal state completely independently, and this same extracted widget then also genuinely becomes reusable elsewhere throughout the rest of your app wherever that exact same specific particular behavior might again genuinely be needed.

class ExpandableSection extends StatefulWidget {
  @override
  State<ExpandableSection> createState() => _ExpandableSectionState();
}

class _ExpandableSectionState extends State<ExpandableSection> {
  bool isExpanded = false;
  // ... build method toggling based on isExpanded
}