How to use the twitter-text.isValidHashtag function in twitter-text

if (!isPresent(label)) {
            return Optional.empty();
        }

        if (!label.startsWith('#')) {
            label = '#' + label;
        }

        const strippedLabel = this.stripTypedLabel(label);

        if ( ! strippedLabel.isPresent()) {
            return Optional.empty();
        }

        if (twitter_txt.isValidHashtag(strippedLabel.get())) {
            return Optional.of(label);
        }

        return Optional.empty();

    }