each as Event.class:
  {"kind":"payment","id":"p1","amount":10.0}
  {"kind":"refund","id":"r1","amount":4.0}
  {"kind":"login","user":"ann"}
  {"kind":"F07SealedHierarchies$Logout","user":"ann"}
round trip equal: true
  payment 10.0
  refund 4.0
  login ann
  logout ann
nested sealed type read as Audit.class: Login[user=bo]