(format stream "~A G {~%graph " (if (contains-undirected-edge-p g) "graph" "digraph"))
(format stream "[")
(funcall graph-formatter g stream)
(format stream "~A G {~%graph " (if (contains-undirected-edge-p g) "graph" "digraph"))
(format stream "[")
(funcall graph-formatter g stream)