how to get entity layout for nav_static_maze*

I am trying to get entity layout for the built-in `nav_maze_*` levels. I found that the `nav_maze_random_goal*` have hard coded the entity layout strings in their lua scripts while `nav_maze_static_*` just create map without layout parameters. What's more, all debug `DEBUG.MAZE.LAYOUT` outputs of those levels are empty. My question is how to get the layout of static goal map in form of string?