getToken(...keys) {
        for (const key of keys) {
            const item = this._tokenizer_config[key];

            if (!item) continue;

            if (typeof item === 'object') {
                if (item.__type === 'AddedToken') {
                    return item.content;
                } else {
                    throw Error(`Unknown token: ${item}`);
                }
            } else {
                return item;
            }
        }
        return null;
    }
Returns the value of the first matching key in the tokenizer config object.
@param {...string} keys One or more keys to search for in the tokenizer config object.
@returns {string|null} The value associated with the first matching key, or null if no match is found.
@throws {Error} If an object is found for a matching key and its __type property is not "AddedToken".
@private