* @return A Promise that will be resolved with the response or rejected with an error.
     */
    public Deferred<T>.Promise execute(final Client client) {
        final String error = getValidationError();
        if (!Strings.isNullOrEmpty(error)) {
            throw new IllegalArgumentException(error);
        }

        final Deferred<T> deferred = new Deferred<>();
        try {

        return concat;
    }

    /**
     * Add a bad word.
     * @param badWord Bad word
     */
    public void add(final String badWord) {
        final String validationError = getValidationError(badWord);
        if (validationError != null) {
            throw new IllegalArgumentException("Validation error: " + validationError);
        }

        if (logger.isDebugEnabled()) {

     * Adds a language to filter by.
     * @param lang The language.
     */
    public void addLang(final String lang) {
        languages.add(lang);
    }

    @Override
    protected String getValidationError() {
        return null;
    }

    // ============================================================
    // Deprecated delegate methods for backward compatibility