fieldcollection.php

См. документацию.

<?php
 
namespace Bitrix\Location\Entity\Location;
 
use Bitrix\Main\ArgumentTypeException;

final class FieldCollection extends \Bitrix\Location\Entity\Generic\FieldCollection
{
    protected $items = [];
 
    public function addItem($field): int
    {
        if(!($field instanceof Field))
        {
            throw new ArgumentTypeException('field must be the instance of Field');
        }
 
        return parent::addItem($field);
    }
}