public function ExportCsv($channelNames, $compressionFormat = \ElasticEmailEnums\CompressionFormat::None, $fileName = null) {
        return $this->sendRequest('channel/exportcsv', array(
                    'channelNames' => (count($channelNames) === 0) ? null : join(';', $channelNames),
                    'compressionFormat' => $compressionFormat,
                    'fileName' => $fileName
        ));
    }