code: protected boolean acceptToString(Field field) {
          return acceptedToStringTypes.contains(field.getType())
                  || acceptedToStringTypes.contains(field.getType().getName());
      }
docs: Subclasses may override this method to include or exclude some properties
  in toString. By default only "simple" types will be included in toString.
  Relations to other domain objects can not be included since we don't know
  if they are fetched and we don't wont toString to fetch them.
  
  @param field
  the field to include in toString if this method returns true
  @return true to include the field in toString, or false to exclude it