document.put("title", "タイトル");

        SuggestAnalyzer analyzer = suggester.settings().analyzer().new DefaultContentsAnalyzer();
        List<SuggestItem> items = defaultContentsParser.parseDocument(document, supportedFields, tagFieldNames, roleFieldName, "lang",
                createDefaultReadingConverter(), createDefaultReadingConverter(), createDefaultNormalizer(), analyzer);

        assertNotNull(items);

            throw new SuggesterException("Failed to create SuggestItem from query log.", e);
        }

        return items;
    }

    @Override
    public List<SuggestItem> parseDocument(final Map<String, Object> document, final String[] fields, final String[] tagFieldNames,
            final String roleFieldName, final String langFieldName, final ReadingConverter readingConverter,

                stream.parallel();
            }
            final SuggestItem[] items = stream.flatMap(document -> {
                try {
                    return contentsParser
                            .parseDocument(document, supportedFields, tagFieldNames, roleFieldName, langFieldName, readingConverter,
                                    contentsReadingConverter, normalizer, analyzer)
                            .stream();