// returns visited objects
// visitor may be null, then it's just about returning the set
static Set philosophyBot1_visitTrailsTree_gen(virtual PhilosophyBot1 engine, IVF1<O> visitor, O startingPoint) {
  new Set seen;
  philosophyBot1_visitTrailsTree_gen(engine, seen, visitor, startingPoint);
  ret seen;
}

svoid philosophyBot1_visitTrailsTree_gen(virtual PhilosophyBot1 engine, Set seen, IVF1<O> visitor, O startingPoint) {
  if (startingPoint == null) ret;

  if (!seen.add(startingPoint)) ret;
  visitor?.get(startingPoint);
  
  if (startingPoint cast Iterable)
    for (O o : startingPoint)
      philosophyBot1_visitTrailsTree_gen(engine, seen, visitor, o);
  else if (startingPoint cast Map)
    for (O o : values(startingPoint))
      philosophyBot1_visitTrailsTree_gen(engine, seen, visitor, o);
  else
    philosophyBot1_visitTrailsTree_gen(engine, seen, visitor, rcall getTrail(engine, startingPoint));
}