code: func Find(ctx context.Context, allowDup bool, f AdvFilter) ([]Advertisement, error) {
  	if defaultDevice == nil {
  		return nil, ErrDefaultDevice
  	}
  	var advs []Advertisement
  	h := func(a Advertisement) {
  		advs = append(advs, a)
  	}
  	defer untrap(trap(ctx))
  	return advs, Scan(ctx, allowDup, h, f)
  }
docs: // Find ...