Method follow

javascript/0355-design-twitter.js:33–37

(followerId, followeeId, { following } = this)

    }

    follow(followerId, followeeId, { following } = this) {
        if (!following.has(followerId)) following.set(followerId, new Set());

        following.get(followerId).add(followeeId);
    }

    unfollow(followerId, followeeId, { following } = this) {
        if (following.has(followerId))