static <T extends ExternalizableGraphElement> Externalizer<T> forAnyGraphElement() {
    return new Externalizer<>() {
      @Override
      public T load(GraphDataInput in) throws IOException {
        return in.readGraphElement();
      }

      @Override
      public void save(GraphDataOutput out, T value) throws IOException {
        out.writeGraphElement(value);
      }
    };
  }
static <T extends ExternalizableGraphElement> Externalizer<T> forAnyGraphElement()