InstanceConfig getInstanceConfig(String instanceName) {
    InstanceConfig instanceConfig = null;
    for (MockHelixAdmin helixAdmin : helixAdmins.values()) {
      if (helixAdmin.getUpInstances().contains(instanceName)) {
        instanceConfig = helixAdmin.getInstanceConfig(null, instanceName);
        break;
      }
    }
    return instanceConfig;
  }
@return {@link MockHelixAdmin} from specified dc
ambry-clustermap/src/test/java/com/github/ambry/clustermap/MockHelixCluster.java