Upgrade a self hosted python package from within a python session

We are developing a python package hosted on our own Bitbucket. So far the upgrade of the package works fine from the terminal :

python -m pip install --upgrade --no-cache-dir git+ssh://git@{package_git_url}

The idea is to let the user upgrade the package from within its notebook as the package development is in early stage. For this we use this method within the package :

def upgrade(self):
        subprocess.run(
            [
                "python",
                "-m",
                "pip",
                "install",
                "--upgrade",
                "--no-cache-dir",
                self.config.PIP.URL,
            ]
        )

But when calling this function within python, it does not upgrade the package in the virtual environment. Hence my question : is it possible to upgrade a python package from within a python session ?

@Klaus D. : beste Man, you rock ! just adjusted the upgrade function as follow :

import sys
from pathlib import Path

   def upgrade(self):
        executable = Path(sys.executable).resolve()
        subprocess.run(
            [
                executable,
                "-m",
                "pip",
                "install",
                "--upgrade",
                "--no-cache-dir",
                self.config.PIP.URL,
            ]
        )

and guess what ? it works. Thanks for your help !