Closing as third-party. But for the record, I suspect the problem here is arising from confusion between standard library modules and third-party packages: the multiprocessing package is not a 3rd party package like NumPy (for example): instead, it's part of Python's standard library.

So multiprocessing doesn't need to be listed in your requirements file and doesn't need to be installed from PyPI: just do an "import multiprocessing" in your script and away you go.