Validate request data via Respect/validation

Question

I'm using Slim PHP Framework and I need to validate POST request payload and I'm using this PHP package Respect-Validation. The idea that I have array ob objects and I need to validate the data inside each object. I used this code for validation

    $validator = Validator::attribute("name", Validator::stringType()->notEmpty())
                            ->attribute("sites", Validator::arrayVal()->notEmpty()
                            ->each(
                                Validator::keySet(
                                    Validator::key("id", Validator::intVal()->notEmpty()),
                                    Validator::key("value", Validator::intVal()->notEmpty()),
                                )
                            ))
                            ->attribute('modules', Validator::arrayType()->notEmpty()
                            ->each(
                                Validator::keySet(
                                    Validator::key('id', Validator::intType()->notEmpty()),
                                    Validator::key('title', Validator::stringType()->notEmpty())
                                )
                            ))
    return $validator->assert($body);

but when I sent the data via postman I received this error. although required data sent in the payload but it still returns error?

{
"statusCode": 400,
"error": {
    "type": "BAD_REQUEST",
    "description": "validations errors.",
    "fields": {
        "sites": "Must have keys `{ \"id\", \"value\" }`",
        "modules": "Must have keys `{ \"id\", \"title\" }`"
    }
}

}

postman error