[ROS2] Using colcon doesn't create any file inside the install/<package>/share directory

edit

My package structure is very simple:

workspace/
           src/
           example/
                        launch/
                        resource/
                        test/
                        example/
                        setup.cfg
                        setup.py
                        package.xml

the problem is that I have defined a launch file inside the launch directory in my package. But running: colcon build --packages-select example (where example is just the name of the package) is doesn't move/create/copy the launch file from the launch directory into the install directory. So install/example/share/example/contains no launch file, which should be there even according to the tutorial about launch files here. In fact, the line:

(os.path.join('share', package_name), glob('launch/*.launch.py'))

from the tutorial above, suggests that the launch.py file should be found inside the share directory of the package. And this is not the case for me. I deleted the build and install directory many times. I run colcon build only, but it doesn't create any launch file inside the share directory. So I can only use absolute path inside my launch file or move manually the launch file inside the share directory. There is a reason for that? Or is the tutorial assuming that you move manually your launch file inside the share directory?

I'm using foxy on Ubuntu 20.04

UPDATE: My setup.py file contains the following code:

from setuptools import setup
from glob       import glob

import os

package_name = 'example'

setup(
    name=package_name,
    version='0.0.0',
    packages=[package_name],
    data_files=[
        ('share/ament_index/resource_index/packages', ['resource/' + package_name]),
        ('share/' + package_name, ['package.xml']),
        (os.path.join("share", package_name), glob("*launch.py")),
    ],
    install_requires=['setuptools'],
    zip_safe=True,
    maintainer='Max Muller',
    maintainer_email='max@infromtik.ca',
    description='Test',
    license='GPL',
    tests_require=['pytest'],
    entry_points={
        'console_scripts': [ 'test = example.robot_prog:main',
        ],
    },
)

Again, I understood the tutorials and the explanation. But or our example, with package name my_python_pkg, this will install all launch files from the launch folder, into ~/ros2_ws/install/my_python_pkg/share/my_python_pkg/launch/ is exactly what it is not doing!!! It creates the launch folder inside the package directory inside the install directory: yes It creates/move the launch file inside the launch directory created inside the package directory in the install directory: no

And I don't know, what's wrong with it. Evening following the tutorial I get the folder launch but no launch files, are inside it