Custom importer and errors

Hi folks!
I'd like to split my package tree into several IDE projects and build a custom
importer to import
     'top.child1.child2'
from the directory
     <python-path-entry>/top.child1.child2/__init__.py
so basically replacing the dots with slashes and having the package content
lying directly in the project folder. I have come up with this:
=== usercustomize.py ===
  1 import sys
  2 from importlib.machinery import ModuleSpec
  3 from pathlib import Path
  4
  5 Loader = type(__spec__.loader)
  6
  7 class IdeHelper:
  8     @classmethod
  9     def find_spec(cls, name, path, target=None):
10         for dirname in sys.path:
11             dirobj = Path(dirname)
12             if dirobj.name == name:
13                 break
14         else:
15             return None
16         origin = str(dirobj.joinpath('__init__.py').absolute())
17         ret = ModuleSpec(name, Loader(name, origin), origin=origin)
18         return ret
19
20 sys.meta_path.append(IdeHelper)
which I'm on the right direction with. Unfortunately, I'm getting errors while
importing a subpackage. With 'import top.child1' the error is
     ModuleNotFoundError: No module named 'top.child1'; 'top' is not a package
whereas with 'from top import child1' the error changes to
     ImportError: cannot import name 'child1' from 'top' (unknown location)
How can I make this work?
Best wishes,
Fabiano