code: func (r *baseCommandRun) retrieveBuildIDs(ctx context.Context, builds []string) (buildIDs []int64, err error) {
  	return retrieveBuildIDs(builds, func(req *pb.BatchRequest) (*pb.BatchResponse, error) {
  		return r.client.Batch(ctx, req)
  	})
  }
docs: // retrieveBuildIDs converts build arguments to int64 build ids,
  // where a build argument can be an int64 build or a
  // "<project>/<bucket>/<builder>/<build_number>" string.