code: public function uploadPreview($fileData, $id)
          {
              $parameters = [
              'query' => [],
              'multipart' => [
                  [
                      'name' => 'file',
                      'contents' => \GuzzleHttp\Psr7\stream_for($fileData),
                      'filename' => 'preview-file',
                  ],
              ],
              'headers' => null,
          ];
              $this->post('v1/media.json/' . $id . '/uploadpreview', $parameters);
          }
docs: Upload a new preview for a media.
  
  Replaces the current preview thumbnails for a media with the supplied one. Recommended image size is minimum 1000px on the longest side. If a PDF is uploaded it will be added as a preview document. This enables users to browse documents directly from within QBank. The maximum recommended file size is 10MB.
  
  @param mixed $fileData the file's data content
  @param int   $id