code: func (r *rescanKeys) unspentSlice() []*wire.OutPoint {
  	ops := make([]*wire.OutPoint, 0, len(r.unspent))
  	for op := range r.unspent {
  		opCopy := op
  		ops = append(ops, &opCopy)
  	}
  	return ops
  }
docs: // unspentSlice returns a slice of currently-unspent outpoints for the rescan
  // lookup keys.  This is primarily intended to be used to register outpoints
  // for continuous notifications after a rescan has completed.