Include content/project root as an import starter

Hi!

Currently I've faced a problem working with imports in two project, where one is submodule of the other.
The situation is as follows:
- There is a repository, e.g "core", which contains shared code for other project which are built on top of it
- There is a project repository, e.g "project", which pulls "core" as a submodule

"core" structure:

core/
|__ code/
|   |__ file1.py
|__ tests/

"project" structure:

project/
|__ core/            <-- (git submodule reference)
|__ project1/
    |__ code/
    |   |__ file2.py
    |__ tests/

The "project1" imports are ok, I can do them like

from core.code.file1 import SomeClass
from project.code.file2 import SomeClass2

But when I'm working with core repository alone, PyCharm can't detect import of type

from core.code.file1 import SomeClass

Thus, I'm forced to use imports like

from code.file1 import SomeClass
# But want to use like below
# from core.code.file1 import SomeClass

It works fine for most cases, but this introduces a problem of double imports, where by importing same class from different modules we are left with two different instances, e.g two instances in this case will be
`<core.code.file1.SomeClass>` and `<code.file1.SomeClass>`.
To solve this problem, I want to make all imports in "core" repository to start with `core.`

So, my main question how do I make imports and autocompletion work in PyCharm IDE to be able to use `core` prefix inside "core" repository imports? Picture of desired outcome (to be without errors):

I've already tried to set PYTHONPATH in various preferences parts (this made code actually run through python console interpreter) and tried to set core as a content root, but it didn't help.

For example, in VSCode such config will make import completion work for core repository:

"python.analysis.extraPaths": [
  ".."
]

Would be glad to hear any other way to deal with above mentioned problem!