rosdep cannot find behaviortree_cpp package.

[hanshans2002]

Hello!
I am struggeling to integrate behaviortree_cpp version 4.0.1 into my ROS2 package. I cannot even pass the first step, which would be including the dependencies in CMakeLists.txt and package.xml.

With rosdep install -i --from-path src --rosdistro humble -y I am always getting the error:
ERROR: the following packages/stacks could not have their rosdep keys resolved to system dependencies: behavior_tree_example: Cannot locate rosdep definition for [behaviortree_cpp]

If I add the behaviortree_cpp_v3 dependencies, there is no problem at all.
Is it somehow not integrated, i.e. do I have to integrate it manually?

Thanks in advance,
best,
hans