How to loading model XML from ros parameter like robot_description in ROS2

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Hi, there. I encountered a problem, I don’t know how to load xacro file into gazebo in ros2

In ROS1, we could load model XML from ros parameter

<param name="robot_description" command="$(find xacro)/xacro --inorder '$(find m_bot_description)/urdf/mbot_gazebo.xacro'"/>

<node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen" args="-urdf -model mrobot -param robot_description"/>

And in ROS2, I've found that the ros2 launch have already supported the command, maybe I guess the launch file could be written as

I hope there is an option something like -param in the code where I type -???, but I only found -file, -topic, -stdin in the spawn_entity.py to load the xml

How could I modify it to load the xacro file?

Thanks in advance!