docs: public String graph() throws Exception {
          ByteArrayOutputStream baos = new ByteArrayOutputStream();
          PrintWriter out = new PrintWriter(baos);
          Injector localInjector = Guice.createInjector(new GraphvizModule());
          GraphvizGrapher renderer = localInjector.getInstance(GraphvizGrapher.class);
          renderer.setOut(out);
          renderer.setRankdir("TB");
          if (!roots.isEmpty()) {
              renderer.graph(injector, roots);
          }
          renderer.graph(injector);
          return fixupGraph(baos.toString("UTF-8"));
      }