code: public void detachMetadataCache(SlotReference slot) {
          MetadataCache oldCache = metadataCacheFiles.remove(slot);
          if (oldCache != null) {
              try {
                  oldCache.close();
              } catch (IOException e) {
                  logger.error("Problem closing metadata cache", e);
              }
              deliverCacheUpdate(slot, null);
          }
      }
docs: Removes any metadata cache file that might have been assigned to a particular player media slot, so metadata
  will be looked up from the player itself.
  
  @param slot the media slot to which a meta data cache is to be attached