Trying to check if a user is followed by another user

Looking at the Larabook series I decided to try the method that the author uses to check if an user is followed by another user. I need this also to write a policy to allow Follows, posting etc... So in my User Model I got these lines:

   /**
     *
     * Get the list of users that the current user follows.
     *
     * @return \Illuminate\Database\Eloquent\Relations\BelongsToMany
     */
    public function followedUsers()
    {
        return $this->belongsToMany( self::class, 'follows', 'follower_id', 'publisher_id')->withTimestamps();

    }


    /**
     *
     * Get the list of users who follow the current user.
     *
     * @return \Illuminate\Database\Eloquent\Relations\BelongsToMany
     */
    public function followers()
    {
        return $this->belongsToMany( self::class, 'follows', 'publisher_id', 'follower_id')->withTimestamps();

    }


    /**
     *
     * Determine if the user is being followed by current user
     *
     * @param User $otherUser
     * @return bool
     */
    public function isFollowedBy(User $otherUser)
    {
        $idsWhoOtherUserFollows = $otherUser->followedUsers()->lists('publisher_id');
        return in_array($this->id, $idsWhoOtherUserFollows);
    }

In my view I put a check to see if the Policy works like this:

@can('temp_check', $i)

$i are the posts from a User that I am showing in the page. I am using this check to allow a user to Post a comment or Follow the user

The policy is like this, please remember that I am using this only to test if it's working:

public function temp_check(User $user, Post $post)
    {

        $Publisher = User::find($post->user_id);

        if($Publisher->isFollowedBy($user)){

            dd($user);
        }
        else{
            dd("no cigar");
        }

What happens then is if I load the page I got this error exception:

ErrorException in User.php line 144:
in_array() expects parameter 2 to be array, object given

So Line 144 is this:

return in_array($this->id, $idsWhoOtherUserFollows);

So I guess that $ $idsWhoOtherUserFollows is being returned as Object by $otherUser->followedUsers()->lists('publisher_id'); So the code from the series is not working, is that because Laravel 5.1 behaves differently from 4.3 ? How would you correct that? Indeed that's a Collection:

dd($idsWhoOtherUserFollows)

returns

Collection {#294 ▼
  #items: []
}