python: "from library import module" works, but "import library.module" could not be resolved

Question

I've got this dts:

Pipfile
module-common\
  __init__.py
  setup.py
  common\
    library-common.py
module-a\
  __init__.py
  setup.py
  functional-module\
    library-a.py
    library-b.py

Pipfile is defined as

...
[packages]
module-common = {file = "module-common", editable = true}
module-a = {file = "module-a", editable = true}

setup.py are defined as

from setuptools import find_packages, setup

setup(
    name="module-common",
    version="2",
    ...
    packages=find_packages(),
    ...
)

and

from setuptools import find_packages, setup

setup(
    name="module-a",
    version="2",
    ...
    packages=find_packages(),
    ...
)

init.py files are empty

I installed all with

pipenv install -e module-common
pipenv install -e module-a
pipenv install

pip list is correctly showing my packages into the dts

so, in library-a I want to use a function from library-common,

but this declaration of library-a fails

from common.library-common import SomeClass
print(f"function return: {SomeClass.function()}")

and results in:

NameError: name 'library-common' is not defined

but if I declare

import common
print(f"function return: {common.common-function.SomeClass.function()}")

I got the correct answer.

what am I missing here? how do I get first notation to work?

the purpose is trying not touch library-a code, leave the imports as they are to avoid refactoring the whole codebase