code: private AlbumArt findArtInMemoryCaches(DataReference artReference) {
          // First see if we can find the new track in the hot cache as a hot cue
          for (AlbumArt cached : hotCache.values()) {
              if (cached.artReference.equals(artReference)) {  // Found a hot cue hit, use it.
                  return cached;
              }
          }
  
          // Not in the hot cache, see if it is in our LRU cache
          return artCache.get(artReference);
      }
docs: Look for the specified album art in both the hot cache of loaded tracks and the longer-lived LRU cache.
  
  @param artReference uniquely identifies the desired album art
  
  @return the art, if it was found in one of our caches, or {@code null}