public synchronized void remove(C callback) {
        if (mNotificationLevel == 0) {
            mCallbacks.remove(callback);
        } else {
            int index = mCallbacks.lastIndexOf(callback);
            if (index >= 0) {
                setRemovalBit(index);
            }
        }
    }
Remove a callback. This callback won't be notified after this call completes.

@param callback The callback to remove.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/util/obs/CallbackRegistry.java