public function deleteUser($uid, $eventTime=null)
    {
        $eventTime = $this->getEventTime($eventTime);

        $json = json_encode([
            'event' => '$delete',
            'entityType' => 'user',
            'entityId' => $uid,
            'eventTime' => $eventTime,
        ]);

        return $this->sendRequest('POST', $this->eventUrl, $json);
    }