code: public static void createMetadataCache(SlotReference slot, int playlistId, File cache) throws Exception {
          createMetadataCache(slot, playlistId, cache, null);
      }
docs: Creates a metadata cache archive file of all tracks in the specified slot on the specified player. Any
  previous contents of the specified file will be replaced.
  
  @param slot the slot in which the media to be cached can be found
  @param playlistId the id of playlist to be cached, or 0 of all tracks should be cached
  @param cache the file into which the metadata cache should be written
  
  @throws Exception if there is a problem communicating with the player or writing the cache file.