docs: public static long getMaxForExtent(PersistenceBroker brokerForClass, FieldDescriptor field) throws PersistenceBrokerException
      {
          if (field == null)
          {
              log.error("Given FieldDescriptor was null, could not detect max value across all extents");
              return 0;
              // throw new PersistenceBrokerException("Given FieldDescriptor was null");
          }
          // first lookup top-level class
          Class topLevel = brokerForClass.getTopLevelClass(field.getClassDescriptor().getClassOfObject());
          return getMaxId(brokerForClass, topLevel, field);
      }