Input graph file format for repartitioning

Hi, all, I found in some old posts in this forum that the format of the input graph file for ParMetis is the same as Metis. However, I want to do a repartitioning. How can I add the existing partitions of each vertex to the input file? Can some one give an example?

I know ParMetis is supposed to be used as a library, but in my case, I only need some black-box experiments. So I do not want to bother writing my own codes calling ParMetis library.

Many thanks!