```dart title="Dart" import 'package:kreuzberg/kreuzberg.dart'; Future main() async { // A Dart implementation of the `PostProcessor` trait that gates on PDF // MIME type cannot be plugged into the global registry. // `Kreuzberg.registerPostProcessor(impl)` exists, but its // `createPostProcessorDartImpl` factory takes opaque `BoxFn*` closure // values plus a `BoxFnDartFnFutureProcessingStage` whose constructors are // not surfaced through flutter_rust_bridge. The `ProcessingStage` enum is // not exported to Dart either. // // Implement the post-processor in Rust as `Plugin + PostProcessor` and // register it via `register_post_processor` in a Rust shim crate. } ```