How to push a bundle of images in parallel

BUILD

load("@io_bazel_rules_docker//container:bundle.bzl", "container_bundle")
load("@io_bazel_rules_docker//container:image.bzl", "container_image")
load("@io_bazel_rules_docker//contrib:push-all.bzl", _push_bundle = "docker_push")

container_image(
    name = "my_first_image",
    ...
)

container_image(
    name = "my_second_image",
    ...
)

container_bundle(
    name = "bundle",
    images = {
        "foo.us.gcr.io/blah:tag": ":my_first_image",
        "foo.us.gcr.io/quux:tag": ":my_second_image",
    },
    visibility = ["//visibility:public"],
)

_push_bundle(
    name = "push",
    bundle = ":bundle",
)