$group_id,
                'group_label' => $group_label,
                'item_id' => $item_id,
                'data' => $data,
            );
        }

        return array(
            'data' => $export_items,
            'done' => $this->isDone($mails),
        );
    }

    function erase( $email_address, $page = 1 ) {
        $mails = $this->queryMails($email_address, $page);

        $items_removed = false;
        $items_retained = false;
        $messages = [];
        foreach ($mails as $mail) {
            if($mail->delete()) {
                $items_removed = true;
            } else {
                $messages[] = sprintf( __( 'A mail with the id %d was unable to be removed at this time.', 'wp-mail-logging'), $mail->get_mail_id());
                $items_retained = true;
            }
        }

        return array( 'items_removed' => $items_removed,
            'items_retained' => $items_retained, // always false in this example
            'messages' => $messages, // no messages in this example
            'done' => $this->isDone($mails),
        );
    }

    /**
     * True if we have more mails to work on still.
     * @param $mails
     * @return bool
     */
    private function isDone($mails) {
        return count($mails) < self::PER_PAGE;
    }
}