docs: protected ClassDescriptor selectClassDescriptor(Map row) throws PersistenceBrokerException
      {
          ClassDescriptor result = m_cld;
          Class ojbConcreteClass = (Class) row.get(OJB_CONCRETE_CLASS_KEY);
          if(ojbConcreteClass != null)
          {
              result = m_cld.getRepository().getDescriptorFor(ojbConcreteClass);
              // if we can't find class-descriptor for concrete class, something wrong with mapping
              if (result == null)
              {
                  throw new PersistenceBrokerException("Can't find class-descriptor for ojbConcreteClass '"
                          + ojbConcreteClass + "', the main class was " + m_cld.getClassNameOfObject());
              }
          }
          return result;
      }