public function set_room_topic($room_id, $topic, $from = null) {
     $args = array(
       'room_id' => $room_id,
       'topic' => $topic,
     );

     if ($from) {
       $args['from'] = $from;
     }

     $response = $this->make_request('rooms/topic', $args, 'POST');
     return ($response->status == 'ok');
   }