public void removeCallback(ResourceCallback cb) {
        Util.assertMainThread();
        if (hasResource || hasException) {
            addIgnoredCallback(cb);
        } else {
            cbs.remove(cb);
            if (cbs.isEmpty()) {
                cancel();
            }
        }
    }
A class that manages a load by adding and removing callbacks for for the load and notifying callbacks when the
load completes.
core/src/main/java/com/bumptech/glide/load/engine/EngineJob.java