adding multiple categories to product

when i add multiple categories tothe product it saves. But when i go to the edit page the categories are removed, so i have to add them again. in the product model i have added this: ' public function category(): BelongsToMany { return $this->belongsToMany(Category::class); } ' in the category model i have added this: ' public function products(): BelongsToMany { return $this->belongsToMany(Product::class); } ' in the ProductResource this code: ' Forms\Components\BelongsToManyMultiSelect::make(name: 'category_id') ->preload() ->multiple() ->relationship(name: 'category', titleAttribute: 'name') // Display the category names ->required() ->searchable(), ' how can i fix this?