@Override
                protected HttpObject filter(HttpObject obj) {
                    if (obj instanceof ResponseHeaders) {
                        final ResponseHeaders originalHeaders = (ResponseHeaders) obj;

                        if (!originalHeaders.status().isInformational()) {
                            // Do not overwrite the headers set by HttpFile service.
                            return headers.toBuilder().set(originalHeaders).build();
                        }
                    } else if (obj instanceof HttpHeaders) {
                        trailerSent = true;
                        if (!trailers.isEmpty()) {
                            return trailers.toBuilder().set((HttpHeaders) obj).build();
                        }
                    }
                    return obj;
                }
A response converter implementation which creates an {@link HttpResponse} when the {@code result} is
an instance of {@link HttpFile}.
core/src/main/java/com/linecorp/armeria/server/annotation/HttpFileResponseConverterFunction.java