Laravel如何更新孩子的关系？

Hi I am new to laravel and fantastically stuck at saving a child table of 1:M relashtip basically I have 2 models dataset which and table_blacklist 1 dataset can have many table_blacklist

now when I trying update a value of the table_blacklist it gives error

Call to undefined method Illuminate\Database\Eloquent\Collection::save()

the below function is in my dataset model(parent)

public function updateTable($id){

    $table_blacklist = $this->table_blacklist()->find($id); //table_blacklist::find($id);
        $table_blacklist->blacklisted =true;
        $table_blacklist->save();
}