[question] how to install a directory to pythondir?

Excuse me:

https://www.gnu.org/software/automake/manual/html_node/Python.html
describe how to package python by automake. I have

    $ tree src/foobar
     src/foobar
    ├──  __init__.py
    ├──  __main__.py
    └──  utils
       ├──  a.py
       ├──  b.py
       └──  c.py

And my Makefile.am contains

    python_PYTHON = src/foobar

After:

    ./configure --prefix=/tmp/abc
    make install

I got:

    $ ls /tmp/abc/lib/python3.10/site-packages

If I

    python_PYTHON = src/foobar/__init__.py src/foobar/__main__.py  src/foobar/utils/a.py src/foobar/utils/b.py src/foobar/utils/c.py

I got

    $ ls /tmp/abc/lib/python3.10/site-packages
    __init__.py __main__.py a.py b.py c.py

I expected

    $ ls /tmp/abc/lib/python3.10/site-packages
    foobar
    $ ls /tmp/abc/lib/python3.10/site-packages/foobar
    __init__.py __main__.py utils/
    $ ls /tmp/abc/lib/python3.10/site-packages/foobar/utils
    a.py b.py c.py

So, how to install a directory to pythondir?

TIA!
-- 
Best Regards
Wu Zhenyu