Laravel 9 Resources adds array key

I'm trying to generate a Resource with the same model. But in the response it adds a key which i don't know where it comes from.

Here is the api call:

Route::get("/definitions/{companyId}", function($companyId) {
    $definitions = CompanyDefinition::all()->where('company_id', $companyId);
    return new CompanyDefinitionResource($definitions);
});  

Here is the CompanyDefinitionsResource.php:

public function toArray($request)
    {
        
        $companies = $this;
        return [
            // 'name' => $this->name,
            'bankBrokers' => $companies->where('type', 1),
            'shippers' => $companies->where('type', 2),
            'accompanyingDocuments' => $companies->where('type', 3),
        ];
    }

and here is the response from insomnia:

{
    "bankBrokers": [
        {
            "id": "cc1abf9e-819b-495d-b632-bc010d3b703d",
            "company_id": "b054b9db-4e7c-4143-89ac-e82aefb8dab4",
            "name": "Yapı Kredi Bankası",
            "type": 1,
            "created_at": null,
            "updated_at": null
        },
        {
            "id": "b78ee82e-4d91-4f45-827f-202eb581b83b",
            "company_id": "b054b9db-4e7c-4143-89ac-e82aefb8dab4",
            "name": "Garanti Bankası",
            "type": 1,
            "created_at": null,
            "updated_at": null
        },
        {
            "id": "ad08e76d-f1ea-43a3-ac11-84685167086c",
            "company_id": "b054b9db-4e7c-4143-89ac-e82aefb8dab4",
            "name": "Akbank",
            "type": 1,
            "created_at": null,
            "updated_at": null
        }
    ],
    "shippers": {
        "3": {
            "id": "cfa9e413-54be-4284-a3ad-3b0c276c0e52",
            "company_id": "b054b9db-4e7c-4143-89ac-e82aefb8dab4",
            "name": "DHL",
            "type": 2,
            "created_at": null,
            "updated_at": null
        },
        "4": {
            "id": "87b4a5c0-f8cd-4481-809e-eee8f2baa72f",
            "company_id": "b054b9db-4e7c-4143-89ac-e82aefb8dab4",
            "name": "UPS",
            "type": 2,
            "created_at": null,
            "updated_at": null
        }
    },
    "accompanyingDocuments": {
        "5": {
            "id": "bc345648-1003-40e0-88ec-8c3db62931bc",
            "company_id": "b054b9db-4e7c-4143-89ac-e82aefb8dab4",
            "name": "Evrak 1",
            "type": 3,
            "created_at": null,
            "updated_at": null
        },
        "6": {
            "id": "fd2a895f-b62d-4db3-928a-1793c141fa5c",
            "company_id": "b054b9db-4e7c-4143-89ac-e82aefb8dab4",
            "name": "Evrak 2",
            "type": 3,
            "created_at": null,
            "updated_at": null
        }
    }
}

As you can see from the result there are "3" - "4" - "5" keys added to the response. Also in "bankBrokers" you can see it's an array but the others are object. Why it could be added and how can i resolve this issue?

Thanks.