is it possible to have a custom attribute with spatie/laravel-data?

Question

I have a really simple Data written as the following

use Spatie\LaravelData\Data;

class FrequencyData extends Data
{
    public function __construct(
        public string $type,
        public bool $hasEndDate,
        public string $repeat,
        public Carbon|null $endDate
    ) {
    }

    // how do I get this to be added to the object
    public function createRRule()
    {
        // do the logic for the rule
        return 'DTSTART:20230510T043520Z
RRULE:FREQ=WEEKLY;UNTIL=20231110T043520Z;BYDAY=WE'
    }
}

What I want to know is, is it possible to be able to have something where when you call

$frequency = FrequencyData::from(request());
print_r($frequency);

instead of it outputting

Array
(
  [type] => recurring
  [hasEndDate] => 
  [repeat] => weekly
  [endDate] => 2023-11-16T11:00:00.000000+00:00
)

it will output me something like

Array
(
  [type] => recurring
  [hasEndDate] => 
  [repeat] => weekly
  [endDate] => 2023-11-16T11:00:00.000000+00:00
  [rrule] => DTSTART:20230510T043520Z
RRULE:FREQ=WEEKLY;UNTIL=20231110T043520Z;BYDAY=WE
)

is that possible?