allo/app/Model/PackageDetail.php

<?php

namespace App\Model;

use Jenssegers\Mongodb\Eloquent\Model as Eloquent;
use Jenssegers\Mongodb\Eloquent\SoftDeletes;

class PackageDetail extends Eloquent {
    //
    use SoftDeletes;
    
	protected $connection = 'mongodb';
    protected $collection = 'form_package';
	
	protected $guarded = ['_id'];

	public function form() {
        return $this->belongsTo('App\Model\Form','_id','_id');
    }
}