Complex ROS2 parameters via undeclared, namespaced parameters

mappings.py

import rclpy
import rclpy.node

def main():
    rclpy.init()
    node = rclpy.node.Node('mappings', allow_undeclared_parameters=True)
    def mappings():
        mappingsParam = node.get_parameters_by_prefix('mappings')
        mappings = {}
        for key, value in mappingsParam.items():
            namespace, name = key.split('.', maxsplit=1)
            if namespace not in mappings:
                mappings[namespace] = {}
            mappings[namespace][name] = value.get_parameter_value().string_value
        node.get_logger().info(f'mappings: {str(mappings)}')
    node.create_timer(1, mappings)
    rclpy.spin(node)

if __name__ == '__main__':
    main()

mappings.yaml

/mappings:
  ros__parameters:
    mappings:
      m1:
        from: "t1"
        to: "t1"
      m2:
        from: "t2"
        to: "t2"
    use_sim_time: false

ROS2 Complex Parameters

ros2 param load /mappings mappings2.yaml