s += "n{object_id} -> n{str.object_id} [label = \"str\"];\n"
s += str.internal_to_dot
s += "n{object_id} -> n{ns.object_id} [label = \"ns\"];\n"
s += "n{object_id} -> n{str.object_id} [label = \"str\"];\n"
s += str.internal_to_dot
s += "n{object_id} -> n{ns.object_id} [label = \"ns\"];\n"