Laravel 5 array formRequest attributes message

I am trying to upload multiple files and everything is working except i cant figure out how to rename validation attribute of array request

Now i am getting (x can be any number as user can pick any number of files to upload )

The documents.x must be a file of type: png, gif, jpeg, txt, pdf, doc.

I would like to get

The document/s must be a file of type: png, gif, jpeg, txt, pdf, doc.

My Request

class CreatePersonRequest extends FormRequest
{
    public function authorize()
    {
        return true;
    }
    public function rules()
    {

        $rules = [ 'name' => 'required|unique:people' ];

        $docs = $this->file( 'documents' );

        if ( !empty( $docs ) )
        {

            foreach ( $docs as $key => $doc )
            {
                $rules[ sprintf( 'documents.%d', $key ) ] = 'mimes:png,gif,jpeg,txt,pdf,doc';

            }
        } 

        return $rules;
    }

    public function attributes(){ //this isn't working

    return [
        'documents.*' => 'document/s', 
    ];
    }
}

I read that i have to do this in attributes but i cant figure out how. Any help is appricated

via Chebli Mohamed