shadows/framework/src/main/java/org/robolectric/shadows/ShadowCarrierConfigManager.java
@Implementation
  protected PersistableBundle getConfigForSubId(int subId) {
    PersistableBundle persistableBundle = bundles.get(subId);
    if (persistableBundle == null) {
      return new PersistableBundle();
    }
    return persistableBundle;
  }
@Implementation
  protected PersistableBundle getConfigForSubId(int subId) {
    PersistableBundle persistableBundle = bundles.get(subId);
    if (persistableBundle == null) {
      return new PersistableBundle();
    }
    return persistableBundle;
  }
Returns {@link android.os.PersistableBundle} previously set by {@link #setConfigForSubId(int)},
or default values for an invalid {@code subId}.