static Status notFoundStatus(String fetcherId) {
        return Status.newBuilder()
                .setCode(io.grpc.Status.Code.NOT_FOUND.value())
                .setMessage("Could not find fetcher with id:" + fetcherId)
                .build();
    }
FetcherID is key, The pair is the Fetcher object and the Metadata
tika-grpc/src/main/java/org/apache/tika/pipes/grpc/TikaGrpcServerImpl.java