How to publish custom ROS messages in action graph(GUI)?

I know there are many kinds of isaac ros nodes which can publish specific ROS topics(like /joint_states), but they can’t publish custom ROS messages.
How to publish a custom ROS message in action graph(GUI)?

I tried to use a sample code(isaac sim doc. 11.4. Publishing in Extension Scripting) , but “/hello_topic” was not published.
================sample code =============
import asyncio
import rospy

rospy.init_node(“hello”, anonymous=True, disable_signals=True, log_level=rospy.ERROR)
except rospy.exceptions.ROSException as e:
print(“Node has already been initialized, do nothing”)

async def my_task():
from std_msgs.msg import String
pub = rospy.Publisher(“/hello_topic”, String, queue_size=10)

for frame in range(10):
    pub.publish("hello world " + str(frame))
    await asyncio.sleep(1.0)
pub = None