Are "resource markers" made for data files?

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Hi all,

I used to the use the ROS1 Python function rospkg.Rospack().get_package_path("my_package") to retrieve data files (e.g. pictures, yaml, audio, urdf, ...) and/or ROS_PACKAGE_PATH environement variable in ROS1 packages. It looks like this is replaced by "resource markers" and ament_index_register_resource is the closest tool to retrieve resource files.

The doc is here but it's unclear to me if these markers are indeed what we need to retrieve data files, and how we use this with ament_python with no CMakeLists.txt?

Also, is there a ROS2 equivalent to roscd?