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THIS API IS NOT IMPLEMENTED YET. SHOWING HERE JUST TO GET THE GENERAL DIRECTION WE ARE TAKING.
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Use useUnMount$() to run cleanup code when the component is removed.
NOTE: useCleanup$() API is similar, but useCleanup$() runs not only when the component is removed but also when the application is paused. Use useCleanup$() for general cleanup code for resources that can't be serialized. In contrast, useUnMount$() is a general notification that the component is going away.