def _get_package_data_output_mapping(self) -> Iterator[Tuple[str, str]]:
        """Iterate over package data producing (dest, src) pairs."""
        for package, src_dir, build_dir, filenames in self.data_files:
            for filename in filenames:
                target = os.path.join(build_dir, filename)
                srcfile = os.path.join(src_dir, filename)
                yield (target, srcfile)
Iterate over package data producing (dest, src) pairs.
product/gradle-plugin/src/main/python/setuptools/command/build_py.py