@Override
  public String toString() {
    if (isShortForm) {
      return "FindCoordinatorResponse(coordinator=" + coordinator + "; senderId=" + senderId + ")";
    } else {
      return "FindCoordinatorResponse(coordinator=" + coordinator + ", fromView=" + fromView
          + ", viewId=" + (view == null ? "null" : view.getViewId()) + ", registrants="
          + (registrants == null ? "none" : registrants) + ", senderId=" + senderId
          + ", network partition detection enabled=" + networkPartitionDetectionEnabled
          + ", locators preferred as coordinators=" + usePreferredCoordinators
          + ", view=" + view + ")";
    }
  }
When the response comes from a locator via TcpClient this will return the locators member ID.
If the locator hasn't yet joined this may be null.
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/locator/FindCoordinatorResponse.java