[graph-tool] Ordering vertex in NestedBlockState.draw()

Hi all, I've been trying to order the vertices on the rim of a NSBM plot such that the labels, say, as integers, of two neighboring vertices are as close as possible. For example, if I have 5 vertices, I'd like them to be ordered 0-1-2-3-4 on the NSBM plot. Is there an easy way to do that? I know that this might have something to do with the 'pos' parameter but I didn't get the expected result after I play with it. Thanks, Tim