Laravel: Create morphs() relationship nullable

php laravel relationship

PHP Snippet 1:

Schema::create('ps_assistances', function (Blueprint $table) {
    $table->bigIncrements('id');
    $table->string('assistance_number', 50)->nullable();
    $table->nullableMorphs('assitanceable');
});

PHP Snippet 2:

$table->nullableMorphs('assitanceable');