private static boolean isVisibleEdge(@Nullable Integer compiledUpNode, @Nullable Integer compiledDownNode) {
      if (compiledUpNode != null && compiledUpNode == -1) return false;
      if (compiledDownNode != null && compiledDownNode == -1) return false;
      return true;
    }
private static boolean isVisibleEdge(@Nullable Integer compiledUpNode, @Nullable Integer compiledDownNode)