How do I reset the ScanStreamTransformer Accumulator? - dart

Question

I am writing a Flutter application using the BLOC pattern. I'm currently trying to search a database and return a list of results on the screen.
The first search will complete fine. The issue is when I hit the back button and try to do a second search. The first search results aren't cleared out. Instead they remain on the screen and the new search results are placed below them.
In a nutshell here's what I'm doing.(I'm using the RxDart library)
1.) Defining input and output streams:
PublishSubject<SearchRowModel> _searchFetcher =
PublishSubject<BibSearchRowModel>();
BehaviorSubject<Map<int, SearchRowModel>> _searchOutput =
BehaviorSubject<Map<int, SearchRowModel>>();
2.) Piping the streams together in the class constructor.
_searchFetcher.stream.transform(_resultsTransformer()).pipe(_searchOutput);
3.) Adding the results to the fetcher stream
results.searchRows.forEach((SearchRowModel row) {
_searchFetcher.sink.add(row);
});
4.) Using a ScanStreamTransformer to create a map of the results.
_resultsTransformer() {
return ScanStreamTransformer(
(Map<int, SearchRowModel> cache, SearchRowModel row, index) {
cache[index] = row;
return cache;
},
<int, SearchRowModel>{},
);
}
From my debugging, I've found that the code in step 4 appears to be the issue. That cache (or the Accumulator) isn't getting reset between searches. It just keeps adding additional results to the map.
I've yet to find a way of resetting the map in the accumulator / cache that works. I even tried completely destroying the streams and recreating them, but the original search data in the SearchstreamTransformer accumulator still persisted.