[graph-tool] Id's, once again

Hi all, I am new here. I looked into the mail archive but I did not get what I was looking for despite old subjects about id's. I have extracted the strongly connected component (scc) from a graph that I built from a transportation network. I want to identify the nodes of the network that are not connected to the scc. I am able to get the index of the vertices in the graph but I did not find an obvious way to get the id's of these vertices to extract them from my original network. Best, F.