docs: private String formatHeader() {
          StringBuilder builder = new StringBuilder();
          builder.append("digraph patricia {\n");
          //      builder.append("graph [ fontsize=30 labelloc=\"t\" label=\"\" splines=true overlap=false ];\n");
          //      builder.append("# A2 paper size\n");
          //      builder.append("size = \"34.4,16.5\";\n");
          //      builder.append("# try to fill paper\n");
          //      builder.append("ratio = fill;\n");
          //      builder.append("edge [ fontname=\"" + FONT_NAME + "\" fontcolor=\"red\" color=\"#606060\" ]\n");
          builder.append("nodesep=1.5;");
          builder.append("node [ style=\"filled\" fillcolor=\"#e8e8f0\" shape=\"Mrecord\" fontname=\"" + FONT_NAME
                          + "\" ]\n");
          //      builder.append("edge [ fontname=\"" + FONT_NAME + "\" fontcolor=\"red\" color=\"#606060\" ]\n");
          //      builder.append("node [ shape=\"circle\" ]\n");
          return builder.toString();
      }