code: public double getCount(K o1, K o2, K o3) {
      if (depth != 3) {
        wrongDepth();
      }
      GeneralizedCounter<K> gc1 = ErasureUtils.<GeneralizedCounter<K>>uncheckedCast(map.get(o1));
      if (gc1 == null) {
        return 0.0;
      } else {
        return gc1.getCount(o2, o3);
      }
    }
docs: A convenience method equivalent to <code>{@link
  #getCounts}({o1,o2,o3})</code>; works only for depth 3
  GeneralizedCounters