anchor.diff:                                 segment_acc=[],
                                  final_acc=[{Segment, F(Acc)} | FinalAcc]},
               Seek = encode(Id, NextSeg, <<>>),
  -            iterate(eleveldb:iterator_move(Itr, Seek), IS2);
  +            iterate(iterator_move(Itr, Seek), IS2);
           _ ->
               %% Done with traversal
               IS
  
positive.code:                _ ->
                     encode(Id, First, <<>>)
             end,
      IS2 = iterate(eleveldb:iterator_move(Itr, Seek), IS1),
      #itr_state{current_segment=LastSegment,
                 segment_acc=LastAcc,
                 final_acc=FA} = IS2,
  
negative.code:             [];
          _ ->
              Result
      end.
  
  iterator_move(undefined, _Seek) ->
      {error, invalid_iterator};
  iterator_move(Itr, Seek) ->
      try
          eleveldb:iterator_move(Itr, Seek)
      catch
          _:badarg ->
              {error, invalid_iterator}
      end.
  
  -spec iterate({'error','invalid_iterator'} | {'ok',binary(),binary()},
  