refactor.php

$csv = Reader::createFromPath(database_path('seeds/sources/belgian-cities.csv'), 'r');
        $csv->setHeaderOffset(0);

        foreach ($stmt->process($csv) as $city) {
            // Create a new province if not exists
            $province = $provinces->firstOrCreate(['name' => $city['province']]);

            // Create a new city in the database if not exists
            $cityInformation = $cities->firstOrCreate([
                // City information
                'province_id' => $province->id, 'postal' => $city['postal'], 'name' => $city['name'], 'lat' => $city['lat'], 'lng' => $city['lng']
            ])->setStatus('pending');;

            // Attach province to the create city 
            $cityInformation->province()->associate($province)->save();
        }