public function listTopics($nextToken = null) {
		$params = array();

		if(!is_null($nextToken)) {
			$params['NextToken'] = $nextToken;
		}

		$resultXml = $this->_request('ListTopics', $params);

		// Get Topics
		$topics = $resultXml->ListTopicsResult->Topics->member;

		return $this->_processXmlToArray($topics);
	}