How to use local dependency in setup.py

Question

How to specify a local path for a dependency package in setup.py the install_requires key

my_workspace
| - my_new_package_root
|   | - setup.py **** my target setup.py
|   | - my_new_package
| - my_packag_root
|   | - setup.py
|   | - my_package

This is usually achieved using pip install -e my_package_root but I want to use the setup.py for that.

setup(
    ...,

    install_requires=['my_package'],
    ...
)

I found this, but it does not tell how to refer to local filesystem

pip3 setup.py install_requires PEP 508 git URL for private repo