let edge_attributes (e, call) =
let attrib = match e with
| (Src _, Src _) -> [`Style `Invis]
| (OptSliceCallers _, _) -> [`Style `Invis]
| (_, OptSliceCallers _) -> [`Style `Invis]
| _ -> []
in match call with None -> attrib
| Some call -> (`Label (string_of_int call.sid)):: attrib