code: @Override
    public Map<K, V> peekAll(final Iterable<? extends K> keys) {
      Map<K, CacheEntry<K, V>> map = new HashMap<K, CacheEntry<K, V>>();
      for (K k : keys) {
        CacheEntry<K, V> e = execute(k, SPEC.peekEntry(k));
        if (e != null) {
          map.put(k, e);
        }
      }
      return heapCache.convertCacheEntry2ValueMap(map);
    }
docs: We need to deal with possible null values and exceptions. This is
  a simple placeholder implementation that covers it all by working
  on the entry.