// head method
                        responseData =
                                client.execute(RequestDataBuilder.newRequestData().head().url(url).weight(urlQueue.getWeight()).build());
                        if (responseData == null) {
                            return true;
                        }

      return new DummyValueReference<>();
    }

    @Override
    public V get() {
      return value;
    }

    @Override
    public int getWeight() {
      return 1;
    }

    @Override
    public @Nullable ReferenceEntry<K, V> getEntry() {
      return null;
    }

    @Override
    public ValueReference<K, V> copyFor(

      return new DummyValueReference<>();
    }

    @Override
    public V get() {
      return value;
    }

    @Override
    public int getWeight() {
      return 1;
    }

    @Override
    public @Nullable ReferenceEntry<K, V> getEntry() {
      return null;
    }

    @Override
    public ValueReference<K, V> copyFor(