"digraph G {\n\tnode0 [label=\"c\"];\n\tnode1 [label=\"b\"];\n\tnode2 [label=\"a\"];\n\tsubgraph U {\n\t\tedge [dir=none];\n\t}\n\tsubgraph D {\n\t\tnode0 -> node1;\n\t}\n}\n")
"digraph G {\n\tnode0 [label=\"c\"];\n\tnode1 [label=\"a\"];\n\tnode2 [label=\"b\"];\n\tsubgraph U {\n\t\tedge [dir=none];\n\t}\n\tsubgraph D {\n\t\tnode0 -> node2;\n\t}\n}\n")
(check-equal?(graphviz(graph-copyg))
"digraph G {\n\tnode0 [label=\"c\"];\n\tnode1 [label=\"b\"];\n\tnode2 [label=\"a\"];\n\tsubgraph U {\n\t\tedge [dir=none];\n\t}\n\tsubgraph D {\n\t\tnode1 -> node0;\n\t}\n}\n")
"digraph G {\n\tnode0 [label=\"c\"];\n\tnode1 [label=\"a\"];\n\tnode2 [label=\"b\"];\n\tsubgraph U {\n\t\tedge [dir=none];\n\t}\n\tsubgraph D {\n\t\tnode2 -> node0;\n\t}\n}\n")