There are other places where authors are specified that could maybe be used to discover authors.
first choice is AUTHORS file in the root of the repository (or AUTHORS.txt, AUTHORS.md, AUTHORS.rst, ...) as it seems to be a standard and is (almost) language agnostic.
same as AUTHORS, a CONTRIBUTORS file often exist
metadata in Python package's __init__.py files: I would not recommend this one for the reason described here, saying that Python developers should not write metadata in source code, and we don't want to influence them doing wrong things.
As stated in https://github.com/Impactstory/depsy-research/blob/master/introducing_depsy.md, authors are taken from author bylines in PyPI and CRAN metadata, then augmented with repositories owners and contributors.
There are other places where authors are specified that could maybe be used to discover authors.
__init__.py
files: I would not recommend this one for the reason described here, saying that Python developers should not write metadata in source code, and we don't want to influence them doing wrong things.