Setuptools: Creating custom command to install selected package dynamically

I have following package tree , I want to install the particular package from src and base (always install with selected package from src). I am trying to create custom command so that using pip I can pass list of packages names to install as follow: pip install setup.py --install-option="--package=package_1, package_2" , so this should install package_1, package_2 along with base package using single setup.py(let me know if I need more at particular package level too) I am following below folder tree.

parent_package
└── src
|    ├── mypkg1
|    │   ├── module1.py
|    │   ├── module2.py
|    │   └── __init__.py 
|    └── mypkg2
|        ├── module1.py
|        └── __init__.py
|
|---- base
|      |----- init.py
|      |----- module1.py 
|---- setup.py
|---- requirements.txt

I have written code as below which is giving an error

from setuptools import setup, find_packages
from setuptools.command.install import install

import sys
# new install class
class InstallCommand(install):
    # pass argument subpackage from pip install to setup.py
    user_options = install.user_options + [
        ('subpackage=', None, None),  
    ]

    def initialize_options(self):
        sys.stdout.write(f"Inside initialize_options--->")
        sys.stdout.flush()
        install.initialize_options(self)
        self.subpackage = None

    def finalize_options(self):
        sys.stdout.write(f"Inside finalize_options--->")
        sys.stdout.flush()
        install.finalize_options(self)

    def run(self):

        if self.subpackage is None:
            sys.stdout.write(f"Inside IF condition--->")
            sys.stdout.flush()
            # install all sub-packages
            subpackages = find_packages() + ['src.'+x for x in find_packages(where='src')]#['src.'+x for x in find_packages('./src', exclude=['*.tests', '*.tests.*', 'tests.*', 'tests'])]
            sys.stdout.write(f"packages to install --->{subpackages}")
            sys.stdout.flush()
            self.distribution.packages += ['src'] + subpackages 

        else:  
            subpackages = self.subpackage.split(', ')
            # print("Install sub-packages:", self.subpackage)
            # install only specific sub-packages
            subpackages = ['src.'+x for x in subpackages]
            self.distribution.packages += find_packages() + subpackages#['src'] + subpackages
        sys.stdout.write(f"packages distribution install --->{self.distribution.packages}")
        sys.stdout.flush()
        install.run(self)

metadata = dict(
    name='my_connector',
    packages=[],
    install_requires=[],
    setup_requires=[],
    cmdclass={
        'install': InstallCommand
    }
    )

setup(**metadata)

Issue :-

After debugging I could see it's always going in my else condition and installing all the available packages. I tried to print flow , I could see it's first going in initialize_options function and making self.subpackage = None causing entering into else part and not in if.

How should I check for subpackage which I have mentioned in command running as follow:

pip install . -v --install-option="--subpackage=package_1,"