The ROS Wiki is for ROS 1. Are you using ROS 2 (Humble, Iron, or Rolling)? Check out the ROS 2 Project DocumentationPackage specific documentation can be found on index.ros.org
Get started at the README.
https://discourse.ros.org/t/new-software-release-py-trees/2046
Wiki: py_trees_ros (last edited 2021-05-09 15:10:02 by DanielStonier)