involved property
final
      An arbitrary vertex involved in the cycle.
Example
final Graph<int> graph = ...;
try {
  // ... something that throws a CycleException ...
} on CycleException<int> catch (e) {
  final loop = graph.findCycle(e.involved);
  // rethrow, or log, or handle the loop in some way.
}
Implementation
final T involved;