laracom/app/Shop/Provinces/Province.php

<?php

namespace App\Shop\Provinces;

use App\Shop\Cities\City;
use App\Shop\Countries\Country;
use Illuminate\Database\Eloquent\Model;

class Province extends Model
{
    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name',
        'country_id'
    ];

    /**
     * The attributes that should be hidden for arrays.
     *
     * @var array
     */
    protected $hidden = [];

    public function country()
    {
        return $this->belongsTo(Country::class);
    }

    public function cities()
    {
        return $this->hasMany(City::class);
    }
}