* @return An optional entity containing the synonym file, or empty if not found.
     */
    public OptionalEntity<SynonymFile> getSynonymFile(final String dictId) {
        return dictionaryManager.getDictionaryFile(dictId)
                .filter(SynonymFile.class::isInstance)
                .map(file -> OptionalEntity.of((SynonymFile) file))
                .orElse(OptionalEntity.empty());
    }

    /**

        form.dictId = dictId;
        validateApi(form, messages -> {});
        final SynonymFile file = synonymService.getSynonymFile(form.dictId).orElseGet(() -> {
            throwValidationErrorApi(messages -> messages.addErrorsFailedToUploadProtwordsFile(GLOBAL));
            return null;
        });
        try (InputStream inputStream = form.synonymFile.getInputStream()) {
            file.update(inputStream);

        verifyToken(() -> uploadpage(form.dictId));
        return synonymService.getSynonymFile(form.dictId).map(file -> {
            try (InputStream inputStream = form.synonymFile.getInputStream()) {
                file.update(inputStream);
            } catch (final IOException e) {
                logger.warn("Failed to process a request.", e);