code: public static int nvgraphSetVertexData(
          nvgraphHandle handle, 
          nvgraphGraphDescr descrG, 
          Pointer vertexData, 
          long setnum)
      {
          return checkResult(nvgraphSetVertexDataNative(handle, descrG, vertexData, setnum));
      }
docs: Update the vertex set #setnum with the data in *vertexData, sets have 0-based index
  Conversions are not sopported so nvgraphTopologyType_t should match the graph structure