Can you please point me to the place in documentation explaining how to use this in a Python module, i.e. in a file I use as an import?

So far I could easily find the if __name__ == "__main__": stuff which is for standalone applications.
What about supporting injection in an 'importable' module?

The use-case: I'm working on an AWS lambda and my code won't ever be run by itself, it will always be imported into another code (which I have no control over) and the lambda handler function will be called from there.
Is there any way to have everything instantiated/injected when my 'entry point function' gets called by external code?

All tutorials seem to be about standalone apps.
But if I initialize dependency injection in my main module (outside of the 'entry point function') then I'm confused about unit-testing.