public function findByAlias($emojiName = null) : string
    {
        if (is_null($emojiName)) {
            throw IsNull::create("Please provide the name of the emoji you are looking for");
        }

        $emoji = strtolower($emojiName);

        if (! array_key_exists($emoji, $this->getEmojis())) {
            throw UnknownEmoji::create($emoji);
        }

        return $this->getEmojis()[$emoji];
    }