func loadReviewers(ro repoowners.RepoOwner, filenames []string) sets.String {
	reviewers := sets.String{}
	for _, filename := range filenames {
		reviewers = reviewers.Union(ro.Approvers(filename)).Union(ro.Reviewers(filename))
	}
	return reviewers
}
func loadReviewers(ro repoowners.RepoOwner, filenames []string) sets.String {
	reviewers := sets.String{}
	for _, filename := range filenames {
		reviewers = reviewers.Union(ro.Approvers(filename)).Union(ro.Reviewers(filename))
	}
	return reviewers
}
// loadReviewers returns all reviewers and approvers from all OWNERS files that
// cover the provided filenames.