let vertex_attributes (s, has_postdom) =
let attrib = [] in
let txt = Pretty_utils.sfprintf "%a" V.pretty s in
let attrib = (`Label txt) :: attrib in
let color = if has_postdom then 0x7FFFD4 else 0xFF0000 in
let attrib = (`Shape `Box) :: attrib in
let attrib = (`Fillcolor color) :: attrib in
attrib