How to credit open source package if I just borrow a function

I’m writing an open source Python module.

Within my code is a function which I have adapted from a function which I found in an other open source package.

If that other package was a direct dependency of my project, then great, I would just list it as a requirement.

However, I don’t want to include that other project as a dependency, because:

1. it does some other things which aren’t relevant to my project, and
2. even if I did include it as a dependency, only to use this one function, the function as it’s written still wouldn’t work as I need it to.

So, how should I give credit to this other package? Is it OK to just list it in an "acknowledgements" section in the README?