code: def update_thumbnail(api_key, api_secret, video_key, position=7.0, **kwargs):
      
      jwplatform_client = jwplatform.Client(api_key, api_secret)
      logging.info("Updating video thumbnail.")
      try:
          response = jwplatform_client.videos.thumbnails.update(
              video_key=video_key,
              position=position,  # Parameter which specifies seconds into video to extract thumbnail from.
              **kwargs)
      except jwplatform.errors.JWPlatformError as e:
          logging.error("Encountered an error updating thumbnail.\n{}".format(e))
          sys.exit(e.message)
      return response
docs: Function which updates the thumbnail for an EXISTING video utilizing position parameter.
      This function is useful for selecting a new thumbnail from with the already existing video content.
      Instead of position parameter, user may opt to utilize thumbnail_index parameter.
      Please eee documentation for further information.
  
      :param api_key: <string> JWPlatform api-key
      :param api_secret: <string> JWPlatform shared-secret
      :param video_key: <string> Video's object ID. Can be found within JWPlayer Dashboard.
      :param position: <float> Represents seconds into the duration of a video, for thumbnail extraction.
      :param kwargs: Arguments conforming to standards found @ https://developer.jwplayer.com/jw-platform/reference/v1/methods/videos/thumbnails/update.html
      :return: <dict> Dict which represents the JSON response.