message: In interactive_graphviz, more complete help command
diff: @@ -168,7 +168,9 @@ void DoHelpCommand() {
  <height> is specified, the new computation contains nodes up to <height>
  nodes above the root.
  help
  - Prints this usage information.)"
  + Prints this usage information.
  + quit
  + Exit the application.)"
  << std::endl;
  }
  