code: public static String getGraphvizString(
        final InjectionPlan<?> injectionPlan, final boolean showLegend) {
      final GraphvizInjectionPlanVisitor visitor = new GraphvizInjectionPlanVisitor(showLegend);
      Walk.preorder(visitor, visitor, injectionPlan);
      return visitor.toString();
    }
docs: Produce a Graphviz DOT string for a given TANG injection plan.
  
  @param injectionPlan TANG injection plan.
  @param showLegend    if true, show legend on the graph.
  @return Injection plan represented as a string in Graphviz DOT format.