code: func newLdbTreapIter(tx *transaction, slice *util.Range) *ldbTreapIter {
  	iter := tx.pendingKeys.Iterator(slice.Start, slice.Limit)
  	tx.addActiveIter(iter)
  	return &ldbTreapIter{Iterator: iter, tx: tx}
  }
docs: // newLdbTreapIter creates a new treap iterator for the given slice against the
  // pending keys for the passed transaction and returns it wrapped in an
  // ldbTreapIter so it can be used as a leveldb iterator.  It also adds the new
  // iterator to the list of active iterators for the transaction.