code: @Override
      protected int doHashCode() {
          final OtpErlangObject.Hash hash = new OtpErlangObject.Hash(7);
          hash.combine(creation, ids[0]);
          if (isNewRef()) {
              hash.combine(ids[1], ids[2]);
          }
          return hash.valueOf();
      }
docs: Compute the hashCode value for a given ref. This function is compatible
  with equal.
  
  @return the hashCode of the node.