For those using Bazel this looks like a pretty helpful example
of developing and releasing a cross-platform Python package with native-libs (C++ in this case).<p>I've wondered for a while how Deepmind manages their (Python & C++) codebase. This is a small window into that I think, and you can see that they're likely using internal 'Blaze' Python rules and rely on the maintenance of compatibility with the open-source Bazel rules. `py_library` is used in `tree/BUILD`, but it is not loaded explicitly as is expected with Bazel these days; the rule definition is loaded by Bazel implicitly.