How can I use rosnode to see nodes within other nodes?

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Hello,

I am trying to run several nodes within the same executable. Here is a minimal example (a shortened version of this tutorial):

#include "ros/ros.h"
#include "std_msgs/String.h"
int main(int argc, char **argv)
{
    ros::init(argc, argv, "node_handle_namespaces");
    ros::NodeHandle node1("level1");
    while(ros::ok()) {}
    return 0;
}

When I run this example, the output of rosnode list is:

/node_handle_namespaces
/rosout

How can I see whether the level1 node is running?