Programmatically get name of the loaded world without a plugin?

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Is it possible to programmatically get the name of the world that gzserver has loaded without a plugin?

gz CLI doesn't seem to help, and gz topic assume you know the name of the world:

$:~/git/aws-robomaker-sample-application-helloworld/simulation_ws$ gz topic --list
/gazebo/default/undo_redo
/gazebo/default/user_cmd_stats
/gazebo/generation_q87tgy8ltp26_world_12/atmosphere
/gazebo/generation_q87tgy8ltp26_world_12/diagnostics
<snip>
/gazebo/generation_q87tgy8ltp26_world_12/wind
/gazebo/generation_q87tgy8ltp26_world_12/world_control
/gazebo/generation_q87tgy8ltp26_world_12/world_stats
/gazebo/server/control
/gazebo/world/modify