should_be_in_subgraph
(*vp)->gv_flags |= (should_be_in_subgraph(*vp)? GV_INSUBGRAPH : 0);
tv->gv_flags |= (should_be_in_subgraph(tv) ? GV_INSUBGRAPH : 0);
new = should_be_in_subgraph(v);
static boolean_t should_be_in_subgraph(graph_vertex_t *v);
assert(should_be_in_subgraph(v) ==