ROS2: how to specify parameter with namespace in python launch file?

edit

It is unclear to me how a parameter with namespace is accessed in a python launch file.

I define a parameter in my node with:

self.declare_parameters(
    namespace="ns1",
    parameters=[("bar", "default_value_bar_ns1")],
)

In my python launch file I'm trying to set a new value for this parameter with:

parameters=[
    {
        "ns1.bar": "new_value_bar_ns1", # this does not work!
    }
],

With this the parameter "bar" in namespace "ns1" remains unchanged.

What am I doing wrong? Thanks in advance.

Minimal working example here: https://github.com/pglira/ros2-answer...

I'm using ROS2 galactic with the official docker image "ros:galactic".