shadows/framework/src/main/java/org/robolectric/shadows/ShadowSubscriptionManager.java
@Implementation(minSdk = LOLLIPOP_MR1, maxSdk = P)
  @HiddenApi
  protected static int getPhoneId(int subId) {
    if (phoneIds.containsKey(subId)) {
      return phoneIds.get(subId);
    }
    return INVALID_PHONE_INDEX;
  }
@Implementation(minSdk = LOLLIPOP_MR1, maxSdk = P)
  @HiddenApi
  protected static int getPhoneId(int subId) {
    if (phoneIds.containsKey(subId)) {
      return phoneIds.get(subId);
    }
    return INVALID_PHONE_INDEX;
  }
Uses the map of subscription IDs to phone IDs managed by {@link putPhoneId} and {@link
removePhoneId} to return the phone ID for a given subscription ID.