public function setAttendees(array $attendees = []) : void
    {
        $iCalAttendees = new Attendees();
        foreach ($attendees as $email) {
            $iCalAttendees->add("MAILTO:$email", [
                'ROLE' => 'REQ-PARTICIPANT',
                'PARTSTAT' => 'NEEDS-ACTION',
                'RSVP' => 'TRUE',
            ]);
        }
        $this->event->setAttendees($iCalAttendees);
    }