How can I import a package from a inside the same package?

I know this has been discussed many times.. however, I've read many, many answers here that did not show my specific use case, and all I would like is an answer that's suitable for this very case. I love Python (most of it), but the import system is IMHO an absolute mess and very, very quirky and tricky to use.

I am developing a package, and I'd like to have a showcase.py module inside of it which demonstrates the use of the package in the exact same manner and syntax that a user would use it from outside the package.

some_dir/package/__init__.py
                 showcase.py

If a user imports my package from a module located in some_dir, he can write import package and use it. Now I'd would like to have this exact same import syntax in my showcase.py module. I tried like many many things, but I cannot get it working. I am fine to amend sys.path if needed, I'd just like to know how to solve this one single problem.

Solution

This is the basic idea. Let me assume that this is the directory structure.

grandparent_folder/
├── gp.py
├── parent_folder/
│   ├── __init__.py
│   ├── parent.py
│   └── child_folder/
│       ├── __init__.py
│       ├── child.py

Now let us see how the other two python packages to be imported in each python script

In gp.py:

from parent_folder import parent  # Import parent.py
from parent_folder.child_folder import child  # Import child.py

In parent.py:

import sys
from pathlib import Path

# Add grandparent_folder to sys.path
sys.path.append(str(Path(__file__).resolve().parent.parent))

import gp  # Import gp.py from grandparent_folder
from parent_folder.child_folder import child  # Import child.py

In child.py:

import sys
from pathlib import Path

# Add grandparent_folder to sys.path
sys.path.append(str(Path(__file__).resolve().parent.parent.parent))

import gp  # Import gp.py from grandparent_folder
from parent_folder import parent  # Import parent.py